Follow up question: Were all "ranks" elected and could anyone be elected or did you need some qualifications?
Eduard M. Dune was a Moscow factory worker during the February Revolution and wrote a memoir about his experiences during the revolution and the subsequent civil war called Notes of a Red Guard. The Red Army was formed out of local militias that were created to provide protection when the government was relatively unreliable during the time. In the large cities like Moscow, factories were set up like small towns with factory employees living, working, and participating in leisure activities together. The militias were formed on the factory level by Bolshevik party members working at the factories. He writes:
...At the suggestion of the factory committee, the issue of the factory guard, or, more precisely, the organization of guards, was put to this assembly. It was decided that the guards should be paid by the administration. We also thought it necessary to establish a separate volunteer workers' militia alone the lines of the voluntary fire brigade, which consisted of workers living on the factory premises and which had been in existence since before the revolution.
Recruitment to the workers' militia was as strict as to any other organization. The candidacy of each prospective member was discussed at a session of the factory committee, and applicants were often turned down on the grounds that they were regularly drunk or engaged in hooliganism or had behaved coarsely with women. The volunteers numbered 150 and were all drawn from among the young workers, with the exception of some three dozen older men. Twice a week we lined up and were taught military drill, tactics, camouflage, and the rifle manual. We had no weapons, we learned the rifle manual using wooden staves. We also marched with these. Ensign Lygzdyn', son of a worker at the factory, was elected commander of the militia.
Throughout the October Revolution and the subsequent Civil War, Officers were almost always card-carrying Communist Party members, with priority given to those who had been in the party the longest. Due to the disorganized nature and lack of training in the Red Army (and white army, for that matter), Party members could be trusted more than the volunteers, and already possessed some degree of credibility. Non-Party volunteers could rise through the enlisted ranks if they proved competent but it became more difficult the higher they went. It was beneficial to join the party as early as possible to accelerate advancement. As the civil war progressed the Red Army became more organized, and as a result the process of advancing rank became less democratic and more formalized. At the end of the Civil war, the Red Army was organized and functioning much like a modern military machine, though it paled in comparison to the established armies of other European nations due to the loss of institutional experience in the fall of the government.
Stalin destroyed much of the institutional experience the military had gained since the Civil War in his Great Purges in the late 1930's, expelling, imprisoning, or killing most of the officer corps in the Red Army. The experience would be dearly missed as the Red Army struggled to function during the Winter War of 1939 and the German invasion of the Soviet Union in 1941.
Source:
Dune, Eduard M., Diane Koenker, and S. A. Smith. Notes of a Red Guard. Urbana: University of Illinois Press, 1993.
The electoral period in the army was a very brief one, and quite a failure all things considered. The sentiments started before the Bolsheviks took power, and although they had endorsed it, they quickly suppressed it upon their control of the reins. The short history of it I will summarize here.
Democratization of the military began very soon after the outbreak of Revolution. In March, 1917, the Petrograd Soviet (although keep in mind this is still nominally the Russian Army, not the Red Army) issued a so called "Soldiers Bill of Rights", which among other things, formally recognized the soldiers' committees and significantly curtailed the power of officers, including doing away with many forms of punishment and curtailing the types of treatment common in the Tsarist military. The order continued to give lip service to the existing military hierarchy, but removed most of the means by which it was maintained and respected.
At this point in time, the medley of parties at the time however meant that just what the order meant was unclear. The Bolsheviks wanted to take the order to the extreme and essentially demolish the existing military structure - Trotsky would remark it was "the single worthy document of the February revolution" - but they were not exactly in the driver's seat yet, so that wasn't a given, as no other party echoed their position. In addition, the Order only was in effect in Petrograd, where officer elections were already being held, but it was not included in Order #1. Order #2 was issued soon after and attempted to better define the limits of the committees counter to the Bolshevik position as well as stress it only applied to Petrograd, and Order #3 followed banning further elections of officers, but neither order seems to have been particularly effective, as elections continued, and the first Order continued to be followed beyond Petrograd.
Further direction from the All-Russian Conference in April attempted to offer some compromises on elections. Those already held were valid, and while moving forward election of commanders was not allowed, units could reject an appointed commander if they had sufficient reason. Things were by no means stable, given competing interests of the High Command and the various parties, but that would be the general lay out until the Bolsheviks made their move that fall. Following this, their earlier extreme position was now put into effect. In December, 1917, rank was done away with, and up to regimental level, commanders were elected. Soldiers congress' elected those for higher level, while specialist positions were appointed by specific positions as appropriate. In practice of course this obviously means that there were still commanders, just that it offered no privilege beyond command in battle. They were in theory to be considered social equals of the men, possess no insignia to mark their position, and so on.
In spite of this, some 8,000 former officers continued to serve in the face of distrust and sometimes outright hostility. These former officers were often the ones appointed to the military specialist positions to best utilize their skills without the "officership" attached, but it wasn't exactly the same, and of course did nothing to breach the glaring juxtaposition of these former officers in the new Workers' and Peasants' Army. In any case election was, obviously, a short-lived process. The Red Army had its real baptism by fire in February when they received a serious drubbing at the hands of the Germans at Narva, leading in short order to the humiliation of the Brest-Litovsk treaty. It was realized that perhaps a former Corporal as Divisional Chief of Staff, or a previous Ensign leading an entire Corps wasn't going to win battles. In the wake, a series of decrees beginning in March walked it back as:
Owing to the absence of military specialists among the workers and peasants, the principle of electivity to positions of command must be balanced, for reasons beyond our control and on a temporary basis, by that of recommendation and confirmation by the leading organs of Soviet power.
In less guarded terms, the Bolsheviks realized that popular commanders weren't always good commanders - Erikson sums it up well that "Elections to the command posts took on the aspects of farce, primitive revenges and low cunning" - and they needed to bring back the professionals, including old Tsarists, who were now actively recruited, although many units continued to select officers at least for another year despite the ban, and it would reoccur even later in sporadic mutinies. Elected commanders who had proven themselves were left, in place, but it was no longer in the soldiers' hands. As evidenced there, the move wasn't a popular one, but it was, in Trotsky's mind, a necessary one. It has been popular with the soldiers, one of the first things that came about with the revolution, but military expediency was simply more important.
Edit: Beaten to it by u/Georgy_K_Zhukov :) I will at least recommend Rex Wade's Red Guards and Workers' Militias in the Russian Revolution as a social history with further reading about the organization and life within Red Guard units in 1917 and 1918.
It's very difficult to say what the "average life" of a Red Army volunteer would be at this point, because we are talking about largely autonomous, ad-hoc units of Red Guards, ex-soldiers and sailors, and partisans.
The Provisional Government's army disintegrated in fall 1917, especially after the disastrous Kerensky Offensive and then the fall of Riga. The Russian army had been in the process of democratization since the February Revolution and the abdication of the Tsar, and especially since a March 14 order by the Petrograd soviet instructing soldiers to form soldiers' councils on the company level upwards and get to rid of many trappings of discipline, such as saluting, shoulder boards, or addressing officers as "Your excellency."
Meanwhile, since the February Revolution, Russian workers had spontaneously formed Red Guard units - local, voluntary militias committed to preserving the gains of the revolution and confronting employers. These were grass-roots movements and class-exclusive. Alone of Russian political parties the Bolsheviks encouraged Red Guards to form but did not actively support them.
But as Russia's internal and external situation deteriorated even further it is not surprising that most Red Guards became to a degree Bolshevized and supportive of further revolution. This had more to do with similar political goals, rather than overt control. Red Guard units of armed workers backed the October Revolution in Petrograd and indeed made the coup possible, securing bridges and buildings for the Bolsheviks, although again not under their direct commands.
After the October Revolution, the new Bolshevik government depended on revolutionary soldiers, Red Guards, and volunteers to the cause (often from abroad) to fight the Central Powers and the slowly-growing counterrevolutionary forces. Soldiers' councils and Red Guard militias formed the nuclei around these units could form. Like the Red Guard units it formed around, the nascent Red Army took the form of a class-based militia.
This meant requirements to join were rather stringent: "To enter the ranks of the Red Army, applicants must have recommendations from: the committees of the sections and democratic social organizations that share the platform of soviet power; party or union organizations or from at least two members of said organizations."
The Bolshevik government officially sanctioned the previous democratization of the army and now took it even further, abolishing officer ranks, while authorizing elections of commanders in platoons on up to regiments. Special soldiers' congresses chose higher-ranking commanders. There were also unit commissars, or political officers, a continuation of Provisional Government practice, with vague orders to police units of counter-revolutionary thoughts.
In practice this is not a very good way to organize your army and it may not be surprising that this military organization proved ineffective. Many groups, like bands of partisans and especially Red Guard units jealously guarded their independence and opposed any attempt to impose higher authority. While there is no doubt many Red Guards were highly politically motivated, they were still poorly trained factory workers with strong local ties and little desire for military discipline or far-off campaigns.
The German army relentless advanced further into Russia, giving much schadenfreude to British military attachés, (despite the fact the Russia remained their ally for the time being). Later that spring a few tiny all-officer regiments of the counterrevolutionary Volunteer Army thoroughly humiliated overwhelming Red forces in southern Russia. The failures of a class-based militia led to the reformation of the Red Army as a much more capable military machine.
I hope this gives some sense of what the Red Army was like before its reformation in the spring of 1918.
Sources:
Francesco Benvenuti, The Bolsheviks and the Red Army 1918-1921
Rex Wade, Red Guards and the Workers' Militias in the Russian Revolution
I don't know if this is ranging too far off topic of the original question, but have there been other military forces that elected their officers and were the results similar?