I'm mostly concerned with cooling issues. What should I look for in a case to be sure it will cool adequately. The system I am building will have an Athlon XP CPU (probably running around 2GHz). Are there any brands to stay away from?
Look for something which will provide a good constant airflow, with as little pockets of hot air build up.
Ideally an intake at the bottom/front of the case and an exhaust at the rear/top, allowing the hot air to rise. Can also mod the case to include chimney exhausts and perhaps an intake on the side over the CPU/chipset/gfx card.
Rather more or larger fans than faster ones, as you can get the same results for less noise.