I'm no expert in the area of weightlifting or nutrition, but I have put on 30 lbs in the past year from lifting. This time last year I weighed 149 lbs. I now weigh around 177-181 depending on how much water I'm carrying. There are a lot of good suggestions in this thread. In the gym, I do agree with doing compound exercises. It is EXTREMELY important to do exercises like the bench press, dead lift, and squats if you want to get big really fast. All of theses exercises work numerous muscle groups all at the same time. You will be amazed with how draining these exercises are. After a good set of deadlifts, you'll feel like you just sprinted a mile. It's also beneficial to do supersets. There are many variations of supersets and I won't get into that now, so just do a google search to learn more about them. But in a nutshell, I basically never take rests between any of my sets. I usually try to do ab or calf exercises between my main sets. I also like to break up my workouts into different groups throughout the week. Instead of hitting every muscle everyday, I'll do chest/shoulders one day, back/legs the next, and arms the day after that. That has seemed to work pretty well for me.
In terms of nutrition, I eat a lot. I try to consume 2700-3300 calories a day. I eat a lot of chicken, turkey, tuna, peanut butter, almonds, wheat bread, and fruits. I need to work on vegetables a little more. I also drink about 64 ounces of water a day. For supplements, I take a good amount of whey protein as well as weigh gainer. The weight gainer gives me a lot of complex carbs as well as some protein. It's an easy way to get about 900 calories. I typically consume about 150-250g of protein, 300-400g carbs and 90g of fat a day. It's important to keep saturated fat levels relatively low (<25g a day). I also take fish oil and green tea extract.
Doing all this has worked pretty well for me. I also only gained about 1% body fat over the past year. Once I hit 195, I will start a shredding cycle to bring down my body fat %. Hopefully this gives you an idea of what it takes to gain a decent amount of muscle mass. Just be patient and don't expect overnight results.