Eat a well balanced diet with plenty of protein. Weight training will do the rest. :)

I would recommend Accai Berry Supplements, Vitamin B12, And Vitamin C. If you want to gain muscle in your thighs, I would recommend doing olyptical machines, biking, rock climbing, or running. There are also machines that work your inner and outer thighs. Also, if you want strong muscles, take power drinks that are powder.

I'm assuming you are a male. I've had some great success using L-carnitine and green tea supplements for burning the fat and speeding up metabolism (not sure if this is true, but that's what I've heard about this combination). Of course, to build mass you need some good weight training. When I used to pump weights, I would lift as much as I could do for around 10-12 reps and do three sets of each exercise. Of course, this was back in the late eighties/early nineties, so newer and better methods for building mass might be recommended now.

It is a common rumor that heavy weight and low reps gives bulk:false. It is common for people to try that theory and end up not focusing on the form because they are just trying to push as much weight as they can. Start out for the first month focusing on perfect form 4-6 sets at 10 -15 reps with the last rep being difficult but not to where you are straining ( if you really don't know what perfect form is, do some research or contact someone educated in the field. I.E.- if you are bench pressing and have to push ya butt off the bench to get the weight up then it is not perfect form. FYI most amateur weightlifters do most of their exercises with incorrect form more or less. I am friends with competing bodybuilders and to gain bulk it is best to switch up weight with number of reps. (i.e. 1 month a weight you can get 6-10 sets of 10-12 reps upper body 0r 12-20 for legs and then another month do heavier weight that you can still get perfect form in 3-6 sets of 5-8 reps upper and 6-12 legs. That is just an example for hitting both slow and fast twitch fibers; some people try to hit both in each workout. Compound exercises are excellent for building size. SQUATS are the single most important exercise for body development. You will not get far unless you do a good squat workout once a week. Try to do your upper body workouts everyother day and legs and/or ab workouts the days between so the muscles can recover easier. Take a day off the day after rigorous workout days like after squat day and try to get 2 or 3 off days a week. Get 4- 6 healthy meals a day. 1.5 - 2 grams of protein per pound of bodyweight a day through these meals and protein supplements. Avoid soy protein. Take a multivitamin. Plenty of Vitamin C. 1-2 gallons of water a day. I also drink a carb supplement during my workout and a protein shake 30 mins after. Get 8-10 hours of sleep a night. This is just some basics. And no way is the only way. Bodybuilders have different techniques and different opinions so my answer may not be a great one to some but I can assure you it isn't wrong.