I speak for the British army in the 18th century, and cannot give too much accuracy on other nations of the time. For the most part volunteers made up the army's demographics. Conscripts did exist in the British army, but never made up a large portion of their soldiers. Even when they pushed for Press acts and actively used conscription it often never amounted more than a few percent of their total amount. Some other countries used conscription for the basis of their armies, but Britain relied on volunteers for their army. The Royal Navy is another matter entirely and I hope someone else can chime in on that subject.

A young man with a farming background or skilled trade would be very likely to make up the army demographics pertaining to former occupation. Often times, recruits with skills such as tailoring, cordwaining (shoemaking), carpentry, smithing, and even hairdressing could find themselves with extra work to do while in the army. It meant extra pay as well as less time in the drilling area. They still had to be soldiers, but when the regiment needed the new shipment of clothes fitted to soldiers the tailors went away to sew and tailor. Similar for shoemakers and cobblers (they are different in this era) in repairing shoes. A soldier with a farmer background did have some advantages that some officers noticed, these soldiers would be used to being on their feet all day and employed in hard labor. I did a small study for my Master's thesis looking up demographics for the British army in the 18th Century. Most soldiers had "laborer" as previous occupation with the rest going into skilled trades. A bulk of the skilled trades pointed towards the textile industry and then tailoring and cordwaining. It would depend on the town or village the recruit came from, as my study looked at Yorkshire and Inverness for the numbers.

Military leaders did care what recruits they obtained and vigorously preferred to have volunteers of a better repute than the often mentioned "dregs of society" as the composition of the British army. General Campbell Dalrymple stated

The first and most eligible by volunteers, the last and worst by a press. By the first method, numbers of good men are enrolled, but the army is greatly obliged to levity, accident, and the dexterity of recruiting officers for them; by the second plan, the country gets clear of their banditti, and the ranks are filled up with the scum of every county, the refuse of mankind. They are marched loaded with vice, villainy, and chains, to their destined corp, where, when they arrive, they corrupt all they approach, and are whipt out, or desert in a month

Bennet Cuthbertson also stated that recruiting parties should beware of those that come to join the army as a means of escaping punishment or those that have dishonorable discharges from previous service. Cuthbertson feared they would corrupt the regiment and bring dishonor to the regiment, and possibly bring danger to other recruits. He also did not want sailors in the army as they are "accustomed to a more debaunched and drunken lifestyle than what a private Centinel's pay can permit." I would like to add that soldiers did not have a perfect reputation of sobriety in this era and had as much trouble in liquor than Cuthbertson would like. In addition, officers feared that conscripts and pressed men would be more susceptible to desertion and discipline infractions, and would create frustration and trouble among the ranks.

However, this did not mean that a recruit with a perfect background would always be let in. They had to meet certain physical and mental requirements. The army had a minimum height of around 5'5" in peacetime but did sometimes change in wartime as recruiters became desperate to fill the ranks. Bowlegged, knock kneed, and splay footed would be least likely chosen as they would have an awkward time marching the way the army wanted. Eyesight mattered as well since the army did have practice of using marks for the soldiers to sight their muskets against. In someway, the army did have a teeth requirement as one needs to have good teeth to bite down on the cartridges. The regimental surgeon would give recruits a full physical to make sure they fit the regiment's needs and requirements. The army also vastly preferred young men from around sixteen to the early twenties, but I have seen some recruits at an older age such as in their forties. Rarely, have I seen older than that.

There is quite a bit that goes into the logistics and equipping of the army. The smallest administrative unit in the British army is the regiment with consideration of its companies that belong to it. On paper, the War Office had the big responsibility of outfitting and equipping regiments, but in reality they did not much more than lay down the standards of quality and quantity that a regiment must meet. The Colonels, which are the regimental leaders, had to furnish their soldiers and used agents in London to do so. These agents provided the means to get regiments their clothes and accoutrements. The clothes still had to fit the standard laid down by the War Office with coats made of wool broadcloth in madder red, beltings made from buff leather, cartridge boxes with 18 holes, etc. The Treasury and Board of Ordinance (which worked through the Artillery) also had responsibilities of providing for the army. Ordinance dealt with the arms for the regiments while Treasury dealt with supply. Supplies included food, camp equipage, but also clothing in some cases. These departments along with others worked together to furnish the army. The departments did have divisions to spread the workload of obtaining equipment.

On the regimental level, regiments had quartermasters and quartermaster sergeants in their payrolls. The quartermaster sergeant is an appointed role that often had a commissioned officer to fill the position with some cases of a non commissioned officer. A commissioned officer had the appointment of quartermaster, usually a captain, and would work with the quartermaster general and the commissary to acquire furnishings. The army's quartermaster general acted in different capacities than a more contemporary one of the 20th and 21st centuries. They did have the role to furnish, but the quartermaster general also had command duties, responsibilities in movement and intelligence, and transportation. However, by the time of the American War of Independence, the role of Quartermaster General became overextended with the amount of duties required in addition to the tasks of commanding. The QMG would do little more than supervisory with his deputies and assistants while technically in control of all equipping, transportation, foraging, intelligence, camp layouts, and more. To contrast the commissioned officer led Quartermaster General's department, the Commissary had civilians employed exclusively. The Commissary had the responsibility of feeding the soldiers, which included procuring food from mills and farms, as well as the wagons, oats for horses, storage, and distribution.

A lot went into the logistics of the army, and would begin to reforms over the century. One between the Seven Years War and the American War of Independence, and another after the AWI. Every regiment or corps had to be equipped to their standards and that made for some tedious work for these departments. It did not always work out though, some shortages did happen, supplies came late or stolen, and even distribution of poor quality supplies.