Tyler started out vegetarian...DH and I rarely eat meat, and meat puree just freaked me out. So we kept him vegetarian until he was old enough to eat meat as a finger food, which for him was after 1 yr. Even after that (and to this day) he didn't eat much meat at all, mostly because as a family, we just don't eat it very often. Sooo...like Rhian said, breastmilk or formula should give him all he needs until you wean onto whole milk. It's a good idea to introduce some of the meat alternatives when they're age appropriate, though. Protein and iron are the main concerns in our house, since Tyler loves fortified adult cereals that usually contain plenty of B vitamins. Good protein sources are yogurt, cheese, cottage cheese, tofu, whole milk, and nut butters. Good iron sources include infant cereal, fortified adult cereals, and beans. That's what I can think of off the top of my head...
A good resource is the book "Super Baby Food" by Ruth Yaron. It's a thick book with a lot of info, but she gives a great crash course in nutrition and focuses on how to raise vegetarian kids.