If you're a spendthrift, you probably have clutter around your house. Sorting through it, selling or giving away lots of it can really be sobering, when you think about how much you spent on it (and maybe paid credit card interest on, too).
Saving can be an active thing too; try to figure out a way to make it a game, or a competition with yourself. Last year I determined to pay off my car loan, so I'd figure out little ways to save money in other places, and then make small payments towards the car loan. It was very motivating watching the balance drop below $10K, then $5K, then $2K. Knowing I was nearing the next milestone towards paying it off made it easier to be frugal and avoid shopping, or figure out a way to save a few bucks so I could kick it over to the loan and race towards a $0 balance.
For me, reading basically every MMM article over the course of a couple weeks really made a mind shift for me. I'm still spendy by the standards of many here, but much more thoughtful about my spending, and money doesn't fly out of my wallet the way it used to.
ETA: As far as tricks go, delaying purchases works wonders. If you're about to buy something, find a reason to walk out of the store (need to comparison shop, see if it matches those shoes I have or whatever). Chances are, you'll forget all about The Thing, and won't be bothered to go back and purchase it later. If you need to go to a store where impulse purchases are likely (I'm looking at you, Target), bring a list, stick to it, and don't browse other sections of the store.