I don't necessarily have a strict budget, but I do track everything I spend. It allows me to easily see the areas I can trim back.

I set aside a small amount every week as spending money to be used for something that isn't a necessity. Whenever I see something I like, I save pictures and information about it to a wishlist and start saving toward it. I've found that waiting a few weeks and "saving up" before making a larger purchase almost completely eliminates the mistakes that can be made with impulse purchases.