As a short introduction to the topic I can recommend the newest "The Great War"-Video on youtube. It's really only a introduction but gives some good starting points for research.

I find it most interesting that Hitler was seen "unfit" for the Austrian-Hungarian draft and shortly after, voluntarily, joined the Imperial(in the exact case a bavarian Regiment) German Army. Another point be the social structure of post war Germany, as the highly militarized (surviving conscripts returning home+Prussian military tradition) society had loads of paramilitary-groups consisting mostly of veterans. Those were so called "Freikorps" which took the opportunity of a weak government (Max von Baden from 9. November on) that was already under "fire" (quite often literally) from right- and left-winged groups because of the seen possibility of an implementation of their desired type of government. The government, without a working military (command/branch), had to rely on the imperial structures and partnered with the "Oberste Heeresleitung"/Supreme Army command to assure them armed backup in case of coups. The Freikorps, as they were non-official forces, weren't regulated by the treaty after the war but strongly aligned at the rightwinged/monarchists spectrum. As losing side of the war and with the war propaganda still ringing (the myth of the imperial army, that they "never lost a battle"/"Im Felde ungeschlagen") they were easily influenced by antisemitism (as reason for the lost war... Yes.. It's called the "Dolchstoßlegende . Also it's completly ignoring every jewish soldier/regiment during WW1 who served in the Imperial Army!)"

WW1 was rather an entry point for Hitler to gain slowly access and contacts within the military and to radical groups. F.e. Hindenburg and Ludendorff were both important figures during and after WW1 and especially Ludendorff joined sides with Hitler to try and remove the early government of the Weimar Republic (the so called "November Criminals"). Also he gained authenticity as a german, who suffered through the war and felt betrayed by the truce and the new government.

I hope this helps you a little. I'm at work at the moment so most of this is written off my mind, if you need sources for parts just PM me or request it in the thread, so I can add them later.(Also: First post, tried to be as exact as possible without books at hand)

Edit: Damn, first post already failed, didn't read 'military decisions'. And heres the second part:

The differences between WW1 military strategy/decisionmaking and WW2 are numerous and would def. exceed your question. So as a private during WW1 Hitler was assigned as a headquarter messenger (which is regarded an often decorated service, because of the close ties to the higher ranking officers/commanders in the field and at the HQ in comparison to the regular soldiers).

The better question to ask would be: How did his experience influence the ideology/person and thus his later actions during WW2? I can't recall a connection that directly links his WW1 time to military decisions he later took. If there are any I would really enjoy reading them :)

If you define what exactly you mean by military decision, because there is atm a thread in /r/history which asked about questionable decisions like: push for stalingrad and delaying the offensive on moscow (diverted forces to attack Soviet forces near leningrad and kiev). If you f.e. include alliance politics/plans esp. before the war starts there would be more plausible connections (Britain as an potential ally, the fatal understimation of the US..)

Serving in the army gave him an overconfidence in his strategic ability. He said paraphrasing " on land I am a hero on water I am a coward." AFAIK he usually deferred to his generals in the beginning and later on as his amphetamine addiction and Parkinson took hold he started taking more control.