Where are you located? Here we usually find some whenever we are driving around, and people are clearing their yards or something. It is kind of a trash brush tree. But there are alot of good woods depending on what you like as far as flavor goes. Hickory, pecan, oak, are some of my favorites. You can do some wierder stuff like apple, sugar maple, But I've never tried those since they aren't natural to south texas.
You can also buy the woodchips from walmart then mix it with charcoal. And put them in the indirect heat box. And I know this may be difficult, but if you're using indirect heat, use a foil sause pan and pour some beer in it, and let that evap, and catch the drippings from the meat then use it to baste the meat maybe add some more brown sugar and liquid smoke (i like a brand called
colgin ) Dang it now I'm getting hungry.