I would throw in my 2 cents but Mael and BoCo have almost published a book between them!
All I have to say is:
Getting big is hard , if it were easy everyone would be huge. Since it is hard, weak personalities resort to drug abuse to gain the mass that is more satisfying and healthy long term when gained naturally.
You must integrate training into your lifestyle, not just tack it on as an afterthought. This is required as training affects eating, sleep, and recreational habits. Having said that, it shouldn't be obsessional. While obession is required when you famialrise yourself with training, it shouldn't really become central to your life, just complementary. Training should provide you with the confidence and strength of mind to enrich life in general.
In brief:
1. If you want to get big you must lift big. You must lift big compund movements such as Squats, deads, bench, presses, rows, dips, chins. Leave the definintion exercises until you have the mass to define!!
2. Sleep. This is rather hard to do. It means limiting nights out on the town and TV watching. It also means learning how to deal with the stress that can affect proper rest.
3. Eat. Carry a notebook and record what you eat, you'll be surprised. Do this to develop dietary discipline as you're less likely to eat crap if you must record it!! Reduce saturated fats and simple sugars. Eat more protein. Try a grazing diet of 5-6 small meals per day.
Do not adopt radical diets such as Aitkens. However, everyone responds differently to radical programs. Remember training is a personal journey, what works for me may not work for you.
4. Enjoy what you do as this will engender enthusiaism for life long training.
When in doubt, squat on.