How can I get brownies to bake evenly?
Oven Temperature

Most ovens keep inaccurate temperatures with respect to your setting. You may be setting it to 350, but it could be baking at 375. I would suggest investing in an oven thermometer. I've seen these for a dollar--well worth the investment.

Baking Vessel

I was surprised to find this out, but the pan color actually affects heat conduction. If you use a non-stick tin, for example, your brownies are more likely to burn. I've seen some people use silicone brownie pans to minimize this kind of uneven cooking.