Originally Posted by ToddTheBod

There's a lot of good stuff in here. Something to think about if you're serious about gaining weight and want to do so "cleanly" is that you might be significantly aided using an app or program to track calories. MyFitnessPal used to be good but now it's bloated and sucks.

Secondly, most people are probably familiar with bodybuilding style "bulk and cut" schemes where bodybuilders gain significant fat and muscle and then diet to lose the fat. This is because their goal is to get huge and they're willing to accept gaining fat to gain as much muscle as possible. If you're not interested in this, you're going to probably want to shoot for something like 500-1000 extra calories a day, which works out to about 1-2 lbs per week. Also, if you've been eating at maintenance, you'll gain a bunch of weight right away when you start eating more because your muscles will fill up with glycogen, and it requires ~3g of water to store 1 g of glycogen.

Another thing you need to keep in mind is that the best way to gain muscle, and really recover from working out in general, is to spread your protein intake out throughout the day, in smaller 20-40g servings.
If you eat little to no protein at all throughout the day and then eat 150g at dinner, your body is going to only absorb about 30-40g of that protein as protein and it's going to turn the rest into sugar/fat, and you'll excrete the excess nitrogen out.

It takes a big spike of leucine to stimulate muscle protein synthesis. Leucine is one of the BCAAs, but it's also really common in all complete proteins. So you can skip the BCAA drinks and such as long as your protein intake is sufficient.