How do I fix cookies that spread too much?

Are you chilling your dough first? That's usually the culprit - warm dough spreads like crazy. Pop your cookie dough in the fridge for at least 30 minutes before baking, and make sure your oven temperature is accurate with a thermometer since ovens can run hot. You might also try reducing the butter slightly or adding a bit more flour, but honestly the cold dough trick fixes it most of the time.