Work out like crazy, do: 4 sets @ 10 reps each set. Use weight you can handle. Don't over do it. Biceps Bicep Curls, Concentration Curls, Cable Curls, Preacher Bench Curls, and Machine Curls. Triceps Tricep Pull Downs, Dips, Tricep Extensions, Tricep Kick Backs, Narrow Grip Bench Presses. Chest Incline Bench, Regular Bench, Decline Bench, Dumb Bell Flies, Cable Flies. Back Cable Pull Downs, T-Rows, Bent Over Barbell Lifts, Dumbbell Lifts, Cable Straight Arm Pull Downs. Shoulders Dumbbell Straight Arm Lifts to the Front and to the Side for Deltoids, Bent over Rear Deltoid lifts, Up Right Rows and Shrugs. Legs Leg Extensions, Squats, Leg Bicep Curls, Donkey Calf Raises, Lunges. Abdominals 100 each: Crunches, Twists, Frog Leg Kicks, Bicycles. To Build Mass: Eat like a pig. Include carbohydrates, i .e, Pizza, Tacos, Fried Chicken, Hamburgers, cake, pastries, doughnuts, etc. after you build mass then you can chisel down. For Lean Mass Consume Egg Whites, Lean Chicken and or Meat, Non-Fried Fish, Fresh Vegetables, and No Sugar Drinks. Consume One of the Following: Muscle Tec, Cyto Tec, Muscle Milk, or Run of the Mill protein powder. Rest: Get 7 to 8 hours rest each night.
Gaining muscle should be able health. Gaining muscle very fast is not very healthy... If you want to get more in shape and build up more then you're going to have to be dedicated and patient. I'm sure you know the rest: Eat healthy and work out.
There is NO "fast" way. When it comes to being buffed "No pain, no gain". If you want to be buffed just so you could look intimidating, I believe you are wasting time and energy. If you want to look buffed because you think girls are going to find you more attractive, I believe you will STILL be wasting your time and energy. (Do you think any of those guys in 1D are "buffed"? Justin Bieber? Even older girls are drooling over those guys! (And it doesn't matter if they are actually "gay") I would NOT take steroids until you are well into your 20's! (And even then you better know what you are doing!) You want hot girls? Become a rock star or at least play and get good at some kind of instrument if you are not doing so already. (Long line for guitar players--Go for bass instead. Drums if you can afford the lessons, and the neighbors and parents can put up with the noise. If you can learn to sing---Duude, you'll have so many girls, you will become gay just so you won't be bored anymore by having so many!
Try to schedule 3-4 lifting days per week preferably with at least 1 day of rest in between. This will allow your muscles time to heal and rebuild before the next workout. When you are trying to gain mass less is more, so your workouts should not exceed 45 minutes.