I'm severely underweight. My goal is to gain 80-100 pounds, and to do so in under 6 months. Not fat though, I want to gain muscle weight. How would I go about doing this
I didn't even bother reading any of the other posts but I will tell you this: You are never going to gain 80-100 pounds of MUSCLE in 6 months.
Ever.
That being said, its just going to be a lot of hard work. Research exercices and construct a routine that will develop your entire body. I've never done pyramid sets but my girlfriend is doing them and she says they work quite well. An important thing is to remember not to work out TOO much. You get diminishing returns.
Invest in good protein shake to take once a day. Keep your meals simple and full of nutrients. Lots of fish and chicken is good. Red meat is okay but if you're trying to get lots of protein you probably don't want to eat lots of it. I tend to stick to the idea of eating lots of carbs for breakfast, a balance of carbs and protein for lunch, and the most protein for dinner, and I always try to have a light protein source before I go to bead(two hours or so before). DON'T try to cut out fats. Your body needs them, as long as they are good. Snack on nuts as they are extremely healthy and a good source of protein. (Not to mention delicious)
And again, remember, you won't gain 100 pounds of muscles in 6 months. You probably won't even gain 20. You'll feel results, but massive change doesn't happen over night. Keep at it and you'll get what you want.
10 pounds for 6'6" is like the bordering on slightly overweight. You can check your bmi here: http://www.nhlbisupport.com/bmi/
your ideal weight is like, 170-200, and 152 lbs is a "normal" weight, so you don't need to gain THAT MUCH dude, i would say 20-30 lbs is probably good, and it's not too hard to gain 20 lbs of muscle mass.
BMI is garbage.
Overweight if he has a lot of fat maybe. I'm 6'1 and 220 pounds. I'm perhaps "slightly" overweight in that I have around 24% bodyfat.