Some thoughtful answers have already been given so I'm just going to focus on one aspect -- the challenges of building muscle as a vegetarian. The important thing to know is that consuming protein is essential for muscle growth and repair. You should also know that not all proteins are equal. Most bodybuilders will tell you that animal protein is superior to other forms. Have you ever seen a large wild cat? Some large cats can eat up to 20 pounds of meat a day and if you've ever seen one up close, you'll notice how lean and muscular they are. They aren't eating carbs. And I would bet these cats, unlike their plumper domestic counterparts, don't drink milk either. So, I happen to agree with those who believe animal protein is superior, but that doesn't mean you can't build muscle as a vegetarian.
As a vegetarian, animal protein is not an option, but there are ways around this. I'm not sure what type of vegetarian you are, but if you're a lacto-ovo vegetarian, for example, you can consume dairy products and eggs, both of which are excellent sources of protein. Milk, cottage cheese, and yogurt contain a fair amount of protein and eggs are the form of protein most easily absorbed by the body.
If dairy and eggs are not an option for you, you can combine certain foods to ensure you are getting a full amino acid complement or what some call a "complete" protein. Amino acids are the building blocks of protein. Nine of the 22 amino acids are called "essential" because the human body cannot produce them; they must be obtained from food.
Some vegetarian foods (beyond dairy and eggs) are complete proteins by themselves. Quinoa is one such example. Many vegetarian foods, however, are not complete by themselves. For example, beans are not a complete protein by themselves, and neither is rice, but beans and rice together form a complete amino acid profile. For other examples of vegetarian food combinations that contain a complete amino acid profile visit: http://www.builtlean.com/2012/10/03/complete-vs-incomplete-protein-sources/.
As for number of meals, you eat, I do think it is good to eat smaller meals throughout the day. I've heard of some eating once every three hours and even once every hour, if you can believe it! If you're going to do that, you'll need to find out what the total amount of calories for the day is and divide that by the number of times you plan to eat. Personally, I find that a bit complicated. I eat when I'm hungry and try to get protein (chicken) and fiber (vegetables) in with every meal, while avoiding empty carbohydrates and foods with no nutritional value. I prefer exercising on an empty stomach and am a late, but true convert to this thing called "fasted cardio." You can read about it here: http://www.bodybuilding.com/fun/is-fasted-cardio-the-best-for-burning-fat.html. If I have to eat before exercising, I prefer what I call "healthy milkshakes." Some might call these "smoothies," but I find healthy milkshake just sounds so much more appetizing. Plus, mine are always made with milk, so, in a way, they really are a milk shake. I usually just blend milk with a banana and protein powder. It is so simple and easy. Nevertheless, if you want more variety, check out the following link for some tasty looking alternatives: http://www.health.com/health/gallery/0,,20356969,00.html.
The last thing, but perhaps the most important, is the amount of protein you consume. I read somewhere that Arnold Schwarzenegger believed that the right formula for building muscle was one gram of protein for every pound of weight, but I have seen others suggest protein consumption as high as 2.2 grams for every pound of weight. The Recommended Daily Allowance is just .8 grams. To read about an interesting study on protein consumption, visit the following link: http://www.bodybuilding.com/fun/maki1.htm. The study isn't geared toward the vegetarian, but this article addresses this subject from that perspective: http://breakingmuscle.com/nutrition/how-to-build-muscle-mass-on-a-plant-based-diet. Personally, I find it really difficult to even consume 1 gram of protein for every pound I weigh, but a few years ago I learned that one body builder's motto was "Protein at every meal." I've tried to adopt that motto myself, but easier said than done.
I think you'll find, overtime, that what works for one person doesn't work quite as well for you and vice versa. Find that formula that works best for you and best wishes as you take it to the next level.
