I'm a big spender. There is almost no such thing as saving when it comes to me. There is one simple rule that I taught myself to help save money:
Keep a stash!
I started an emergency stash in my room. I used a piggy bank, but I used it for not only my change, but for bills as well. When I was given money or had any bills leftover, I would take some of the bills, fold them up, and stick them in the piggy bank so that when I had to open the piggy bank, they would be easy to get out. There would be $20 bills on the inside of my piggy bank that I had forgotten about because I had put so much on the inside of it. When I needed cash for an emergency such as a bill needing to be paid, I would dump some of the money out of the piggy bank and use it to pay. I still use this method to save money now. Unless I absolutely need something, I will not open the piggy bank. Since you don't see the money in your wallet, then you start to forget that you have it and that makes you lose the urge to spend it.