Welcome to the forum!
If you look here: http://www.smokingmeatforums.com/t/58778/char-griller-smokin-pro-with-firebox-mods you will find many of the helpfull mods you can make to your smoker (fairly cheap), that will make your overall experience much more enjoyable. The Lowes/Home Depot offsets are generally a good place to get your feet wet, but they do need to be modified a bit to work well. Now for heat, the first thing you want to do is make a charcoal basket, you fill the basket about 3/4 full with unlit charcoal, then you dump about 1/2 a chimney of lit charcoal ontop of that. This is called the minion method, and it will provided long steady heat for several hours. For the wood smoke (flavor wood), use either a small stick or fist sized chunk of flavor wood (hickory, mesquite, cherry, apple, ect.) and put it just to the side of your lit charcoal - add a chunk of wood about 1x per hour or so depending on how strong of a smokey flavor you want.
Make sure any wood you use is dry and well seasoned, if your wood is green it will create creasote, which will ruin the meat and you will have to scrub out your smoker and re-season it. Spend some time poking around the charcoal smokers forum and read up on what folks are doing with their horizontal offset smokers and you will get some great advice.