It sounds simple, but in order to maximize your potential to stay in your budget, ask yourself "Do I really need this?" when your making a purchase. More often than not, once you think about it, you will realize you can do without it for a little while longer.
And, if you are able to, each time you receive your paycheck, take whatever money was left over in your checking account and put it in savings. I use the $25 increment rule. If I have $60 left in my checking when I get paid, I take $50 and put it in the savings.