Alls I knows is...  you just need to eat more than you burn.  I hated hearing it too cause it sounds so retardedly obvious, but just eat carbs (cause they're cheap) in snack form, save the meats for meals.  I heard that 3 big meals a day is worse than like... 8 small meals a day in terms of gaining weight, but I also heard the opposite.  Having more smaller meals makes more sense to me, but whatever.  Work out, of course, and confuse your muscles so that you don't plateau and you'll be able to do more weight and look better.  When I say confuse your muscles I just mean that one week you do hammer curls, the next week you do full supination curls, and so on and so on.  You'll work out different regions of the same area gradually making you bigger.  If you want to get big fast use that workout routine that Feld was talkin about cause it has options for different workouts and has a schedule that's short and makes sense for giving your body time to rest.

Body weight exercises offer little resistance. Eventually you'll need to add more weight (resistance) so consider joining a gym.

You're wrong, dude. Like, you're wrong. I don't mean to sound like an ass, but you're pretty fucking wrong!

Adding weighted vests/etc to the equation add fairly good results.  This being said its not the best exercise you can do obviously.

Of course. That's what I said, eventually you'll need to add up some weight to continue making these exercises effective. Dip belts are super effective for every kind of pull-ups/chin ups whatever and of course dips. As for push-ups you may use loaded bags or whatever. You just need to get creative. ;)

And as it was stated before, they're a good start. But that's about it, they should be mixed along with some other exercises (weights) in order to see even more results. For example, one could have a chest routine that consist of bench press, incline press, dips and pushups and that could be fairly good. My point is, they're a good exercise, but they're aren't one of the best exercises out there.

And certain muscles only show up when they're used in a routine that consist of m any muscle groups. For example, I could never see my abs until I started workin my back and legs more (squats, rows). Using more muslces burns even more calories.