When I bake my date cookies they spread out and don't get high.  They are very thin.  I follow the recipe but this happens.  There is baking soda and baking powder in the recipe.  Any suggestions? 
Substituting half of the white sugar for brown sugar should work, but I've found that if I'm making a lot of cookies the temperature of the room rises due to the constant heat leaking from the oven.  The problem with most recipes is that they assume that the dough and oven remain at a constant temperature and don't account for baking multiple trays of cookies with hot baking sheets, hot kitchen, etc.  First, make sure that you're using softened butter and creaming it properly with the sugar.  I use a regular fork and press the butter and sugar together (if you have a pastry blender, even better).  I know too many people that have your problem because they microwaved the butter until it became oil x_x  Second, if the room is a bit warm and the dough has a sort of slimy texture try sticking the dough in the refrigerator for an hour or so.  Make sure that the dough is sealed airtight so that no nasty fridge smells mess up your cookies -- I use cling wrap pressed tightly against the dough in the bowl.   