I eat a lot of beans and rice and soy protein. getting protein as a vegetarian is easy.
many vegetables have protein to. you just have to know what to complement them with to get complete protein. and i don't shoot for perfectly complete anyway, as long as i get enough. i'm aiming for high arginine.
i'm not a vegetarian though. i have whey protein, drink some skim milk, eat canned mackerel, and microwave an ounce of lean beef every once in a while.
The most important part of building muscle is to do get 60% carbohydrates, 20% non-saturated fats, 20% protein, and eat 4-7 small meals per day, with this calory break down in each one, and a good snack before and after a hard workout, with some fruit juice after. Get 90 grams of protein per day, and don't try to get more than 25 grams per 3 hours because you will not absorb it.
and you need plenty of water to break down the amino acids in your stomach.