I'd add that you need to make sure that the protein is spread out throughout the day. The body doesn't store, so too much at once just becomes extra calories, and not enough at other times leaves your body without the ability to build muscle tissue as a response to your work outs.
I'd make sure you get a good slow-digesting protein before bed, and get some protein with breakfast. Make sure you get some in your system before working out, and use a post-exercise recovery drink immediately after your work (if you've been reading articles on this site, you'll have been told many times about the sponsor's recovery drink, Surge).
I actually like to sip some in addition to a lot of water during training. The key is to spike your insulin at a time when your body's muscles are very ready to put to good use the sugar and protein that insulin helps transport into cells.
Adding to skidmark's comment, you need to be at a slight caloric surplus daily to build muscle. While you don't want to go overboard on the calories, as for non-beginners you can only add a bit of muscle a day, and then you are just adding fat.
To build a pound of muscle a week, you will need to add about 2,500 calories surplus to your weekly diet, or about 350/day. You might want to log your eating (it isn't just for those who want to loose weight), although most of us underestimate how many calories we get without logging, so you are probably getting enough.
If you find that if you are giving yourself enough recovery time, eating protein spread throughout the day (esp. before bed and after a workout), and feel like you are still not gaining a reasonable amount, add an additional snack of good carbs and fats, and make sure part of this is at bedtime (some low-glycemic fruit [e.g., apples, pears], some cottege cheese, etc.).