The Paleo diet is the new thing I'm starting to see some people adopt. They have had great success with it while of course incorporating some kind of fitness routine with it. You should definitely look into it. While it is similar to the Atkins diet there are also differences between them.
This link sums up the diet pretty well.
http://robbwolf.com/what-is-the-paleo-diet/
Here is a good link describing some of the differences between the Atkins.
http://www.paleoplan.com/2011/11-17/...r-than-atkins/
I'm no nutritionist but I know when I was trying to lose weight in High School, I followed what I believe to be the most simple and basic principle that worked for me that twisted squid mentioned.
"6. Burn more calories than you consume."