Read this link, the BBQ FAQ. There are a lot of good tips in there to help.
Number one issue is just what you said, heat control. I wouldn't even worry about meat until you can run it a few hours and have the temp hold a reasonable range. Once you have the temp stable, then I would also map the smoker to find out where the temps are at within the smoke chamber, on the actual grates. A good remote themometer, take it and poke it through a potato (to hold the probe off the grate). Place the probe and multiple locations and see how that temp matches the temp on the smoker. Oh, and don't trust the temp on the smoker without checking it against all these settings. Those smoker thermometers are famous for not being even close.
Here's the link, lots of great info:
Especially chapter 7:
BBQ FAQ Table of Contents