1. Baking Powder

Whichever recipe you're using, don't use baking powder in the dough. I used to take it out only for more detailed cookies, now I omit it all the time.

2. Oven Temperature

Check to make sure your oven really is at the right temperature by using an oven safe thermometer.  If your oven isn't hot enough, the cookies don't 'set' quick enough, and the cookies have more time to spread. Also remember that opening your oven up to peek on the progress of the cookies, will make the oven lose heat and affect 'cookie spreadage'..

Read more at: http://sweetopia.net/2011/04/top-8-tips-on-preventing-cookies-from-spreading/