When it comes to structuring the best training program for skinny guys looking to bulk up fast, there are 7 things you need to work out.
How to select exercises: Choosing exercises that use free weights and bodyweight is the best way on how to bulk up fast. Never use the machines. You need a good range of motion to strengthen muscles and joints. Also go for the heaviest weights that you can lift over 5-8 reps.
How many sets per workout: Skinny beginners do well with low volume. All you need is 12-16 sets per workout to get fast results. Low volume training has several benefits over high volume training. There's no chance of overtraining, you recover well and allow your muscles to grow in the recovery intervals, and you don't feel sore as with high volume training.
How many sets per exercise: Most intermediate and advanced exercisers are recommended 1-3 sets per exercise. However beginners need to do 3-5 sets to get going especially if they are not used to exercising.
How many reps per set: The range of 8-12 reps that you see in many muscle building programs is not for skinny guys trying to bulk up fast. For you, the range of 5-8 reps is ideal. You can lift very heavy weights with this range which is essential for hypertrophy (enlargement of muscle cells).
How much rep speed: Slow is not the way to go, especially for hard-gainers. Speed up lifting and control lowering of weights. Lift in less than a second and lower in about 2 seconds. Slow and deliberate motion is not for skinny guys wanting to put on muscle mass.
How much rest between sets: Beginners can take very short rest intervals between sets - 45 to 90 seconds depending on the exercise being performed. As you grow in strength, endurance and muscle size, you'll need much longer rest - 2 to 4 minutes to allow for better recovery.
How long to train in one session: Never go beyond 30-45 minutes in one session. This is the optimum duration of a training session for testosterone to build up to peak levels. Any more than that and cortisol (catabolic hormone) will start eating away your muscle tissues.