Diet and exercise talk always fascinates me because my dad is an exercise and wellness physiologist. He has seen lots of fads and fashions come and go for decades, but the same ideas always hold true:

Burn more calories than you eat; or eat less calories than you burn
Keep the metabolism going - diet without exercise is asking for more fat after the "diet" is over
Fat content matters
Cardio is king
Weights build strength and endurance - if you want bulk, go for less reps and more weight; if you want linear build - go for less weight and more reps
Never - never - cut out an entire food group
Ant diet that uses a drastic change in body chemistry to give you quick results is asking for trouble

One of the best nutritional diets is the one recommended for diabetics.

I followed the above several years ago, and I lost 35 pounds and kept it off for quite awhile - until I began evil bipolar meds and stopped walking (it was a trigger for H)