Wow...this can be a huge topic. I'll give you a few quick tips, then some places to look for some more info. First off, the latest issue of the
Performance Menu has the best article on this that I've read. You should definitely check it out.
First off, in order to grow, you have to have two things in place: 1- resistance training, which will stress your muscles causing them to adapt by growing bigger, and 2- an increase in caloric intake that will allow extra energy to go towards this muscle growth.
As far as resistance training goes, you can make gains with bodyweight calisthenics and gymnastic skills, but I feel that lifting weights, whether dumbells, barbells or both is the most efficient way to go about this step. Having incremental load increases is a big help when you want to track progress and it allows you to progressively overload your muscles in a linear fashion with a better idea of how much you increase each time. Stick to the big, compound movements; deadlifts, squats, overhead press, cleans, push presses, rows, weighted pull-ups etc. The average rep-range for hypertrophy is between 6-12 reps or so...though gettting much over 10 will be better for recovery days to work out lactic acid, etc. I would suggest hitting 4-6 sets of 6-8 reps of each movement at around 80% of your 1-rep max for a few weeks, increasing the load each week, then taking a back-off week. This is basically the program that they outline in the P-menu article (yes, another plug, it really is that good, and it's only 5$ for a back-issue or 25$ for a yearly subscription....well worth it)
Now, the nutrition side can be a bit more complicated. This can be greatly simplified if you follow a few steps. You have to figure out your daily caloric needs as far as maintaining lean body mass. I have found no better system for this than the Zone diet by Dr. Barry Sears. Once you figure out the weights and volumes of common food and dial in your blocks for the day you have an exact measurement of what it takes to maintain activity level and body-mass. From this point it's just a matter of adding a few extra blocks of protein each day which will allow you to put on some lean mass while minimizing fat-gain. All-in-all, try to stick with "clean" foods such as fruits, vegetables, lean protein and whole grains.
If you get those two aspects dialed in, it's just a matter of getting adequate rest and using recovery to your advantage (i.e. contrast hydrotherapy, 8-9 hours of sleep, keeping stress levels low). If all of these things are in place and you really dedicate yourself to working as hard as possible on a good weight program, a solid nutritional program, and a dedicated plan for intraworkout recovery, you will be able to put on some weight.
Once again, check out the P-menu, as it answers all of these questions in even more depth. If you have any more specific questions, post up! If you want to outline your training and nutrition as it is now, I'd be glad to give you some critiques. Good luck
