Here's my motivational tricks:
1. Just do it!

The hardest part of any workout is the beginning. I find that if I can just get through the first few beastly minutes then I actually start to enjoy it.
2. Make it a habit! It takes exactly three weeks to make something a habit. Do it around the same time every day- try to determine when you have the most energy (and when you can fit it into your schedule). Plan your meals so that you can maximize your own energy level.
3. Stretch! If I take time to stretch before and really get in touch with how my body feels, and stretch out afterwards, I feel much better. It's nice! Plus, I've done yoga, and I love the way it teaches you to be in tune with yourself, and explore your body, instead of just hating it and doing things TO it, do things WITH it.
4. Do something you enjoy. Don't force yourself to walk miles on a treadmill if you've tried it for a while and STILL hate it. Walk outside, or try aerobics, or a stationary bike! I personally would rather be outside, but on hot sticky summer days, of course I prefer a nice cool gym.
5. Try something new! I NEVER liked running. Ever. My dad is a big runner, and I finally got the nerve to just force myself to do it. Of course I really sucked at first, and I couldn't go far at all, but gradually increasing it I got up to running 2 miles at a time with my dad, which was a HUGE accomplishment to me! We were even planning on doing a 5k before heart problems forced me to quit. The point is, I ended up loving the challenge and the way I could use my body to accomplish things that made me feel good about myself.
6. Bribe yourself. Pick your favorite snack for the day (mine would be nuts, or a lemon pie cupcake), and plan it for the latest time possible. Tell yourself if you don't work out first, you don't get it- and follow through. Sub a less-thrilling snack if you don't finish your workout task.
7. Reward yourself! Make a sticker chart! It sounds dorky and childish, but at the gym there was a chart for new years resolutions and I looked forward to putting a smiley face by my name every day.

I've even made one at home and got myself some cute stickers so that I could see the progress- when you're feeling down, or slip up someway, all you have to do is look at the ever-growing line of stickers to assure yourself you ARE doing well! Also, you can come up with non-food related rewards- "If I stick to my exercise plan all week, I will give myself a nice hot bubble bath and pampering day. If I follow it all month, I will buy myself a nice new workout outfit (or jewelry, or shoes, or book, etc.)"
Hope this gave you some ideas!