Take a good look at the diabetic diet. Even if you don't have diabetes (I do), it's a good way to eat. You'll be eating a balanced, healthy diet for the most part.
I used to walk about five miles a day, several times a week. That helps keep weight off, too.
Finally, don't try to lose more than about two or three pounds per week. Taking weight off slowly tends to keep it off, so then you won't do the yo-yo thing.
Hope I helped...and congratulations on what you've accomplished so far!
Eric