hay unwin okay there is some stuff you shoud check out go on to you tube you can find anything from how to mod halo3 to glitching halo3 for you being a new to halo3 you shoud get started with glithcing then go on to what ever i could help you if you help me.
theres not many major glitches in the game like in halo 2. But as everyone else said check youtube and this halo 3 glitches section and youll find a decent amount.
I could. But check out CMNier's channel. He I who I learned most of my glitches off of. I don't know him but I've seen amost all his videos GT ronnoceel