Firstly, thanks for taking an interest in Doom modding. 

If you're new, the best way to learn is to take apart a mod that someone else made and see how it works and it looks like you're on the right track. Below is a list of files with decent commenting that should be good to go through for a first-timer or intermediate modder:
	- actors/babel_monster_base.txt
	- actors/monsters/lostsoul.txt
	- actors/monsters/hellknight.txt

If you're just here for the nifty bits, it's likely you want one of the following files:
	- actors/babel_monster_base.txt
	- actors/babel_projectile_base.txt
	- actors/babel_static_functions.txt
	- actors/babel_tracers.txt
	- actors/babel_weapon_base.txt
	- actors/gibs.txt
	- actors/casings.txt
	- actors/player/base.txt
	- actors/items/armor_wrappers.txt
	- actors/items/large_ammo.txt
	- actors/items/large_health.txt
	- source/HUD_AND_TRACKER.txt