Well explaining may give you some what experience to knowing the basics of what the buttons do but you'll have to actually personally play the game in order to get practice and get used to the controls better and gain better accuracy, eye and hand coordination. Go here below:
http://www.microsoft.com/silverlight/halo3.aspx
^You'll need to download the Silverlight program in order to view the interactive online Halo 3 manual. It shows you all the basic controls, etc and information on the game. Good luck! Have fun.