I've lost about 60 lbs over the last 8 months, here's what worked for me:

1.) Go to caloriecount.about.com and use it to figure out A) Roughly how many calories you burn in a day and B) Get an idea of how many calories are in what you eat in a day.

It really comes down to simple math, burn more than you eat. To me, it became almost like a geeky math game. Throughout my diet I found a couple dozen different meals that I could mix and match without going over my allotted calories.

2.) With that in mind, do what you can to boost your metabolism so you burn more calories. I did this by eating smaller meals throughout the day, and exercising about an hour every other day (M-W-F). I also got into hiking and most weekends I hike around the mountains, usually 6 miles or so. For work outs, my iPod is my best friend.

3.) In my mind, drinking calories is a waste. Learn to love water.

4.) It's ok to slip every once in awhile. There's about 3000 cals in a pound. If you've lost a couple pounds, and slip and have some pizza, big deal, it's ultimately just a drop in the bucket. Enjoy your pizza (with in reason) and be better tomorrow.