I have really been watching what I eat. I started out doing a very low carb diet, but realized that it wasn't the right plan for me since I'm not a huge meat eater!! Then I just started counting calories and watching portions. I loosely follow the nutrition guide and modify it to include some of the foods I like and exchange things out that I don't care for.
The best advice I have that has taken me the longest to develop is accountability. If I have a day that I eat out of control or take an extra helping of that spaghetti, I make sure to remember that when I go to work out next and work extra hard or I go for a workout on an off day!