It all depends on what you want. At 5'10, I'd rather be built like a 340 lb defensive lineman than 180 lbs trim and toned. I'm currently neither.
It's already been said, but Stronglifts 5x5 has worked well for me. High Protein is important. Make sure to get in lots of vegetables too.
Also--this is just from what I've read, I'm no expert--the comment earlier about eating 3-5g of Carbs per pound per day is a path to diabetes. 100-150g of Carbs were usually put up to be more than enough in most of the studies I've seen. Do your own research though.
Check out: http://www.scrawnytobrawny.com/
There is a book (under resources) and a coaching program.
Dr. John M. Berardi is the co-founder and Chief Science Officer of Precision Nutrition Inc. and a former scrawny guy who gained over 70 pounds of muscle. One of the world’s foremost experts on sport and exercise nutrition, Dr. Berardi has coached hundreds of elite athletes — from NFL players to UFC champions — and has helped thousands gain muscle through his writing and coaching. He serves as a high-performance consultant to Nike.
Train for strength. No bodybuilding. Training for "looks" is what boys do. Men train for functional strength.
So how do you gain functional strength? Train a few basic exercises involving as many muscles as possible. Deadlift is #1 for functional strength, closely followed by the squat. Then you need a pressing exercise or two for the upper body. In my opinion the best are standing 1-arm presses and dips. But more important for functional strength is upper body pulling ability, and here shoulder-grip chins with palms facing is best, supplemented by a rowing exercise. And let's not forget grip. If you can't grip it, you can't lift it! Go to ironmind.com and check out their grip gear.