The key to any diet is balance. There is nothing exclusively in meat that cannot be obtained in a vegetarian source. You want to vary the foods you are eating, remember that different foods(grains, beans, fruits, etc) often mean different nutrients, as well as different colors within these groups(yellow, greens, reds, etc). You don't want to eat all green veggies, and avoid yellow, purple, etc. For example, if you are making a mix vegetable stir-fry, don't just use one color(broccoli, spinach, etc), vary the colors(red pepper, yellow squash, spinach, etc).
The other key to a good diet is education. Know what different foods are providing for your body. Read through as many books, web pages(credible ones) as possible, and speak to a knowledgeable dietitian.
There are some web pages that can give you an idea about what nutrients are in what foods, so you may want to use them as a reference. Personally I like the web page
http://health.discovery.com/national-bod… . It offers the option of setting up a menu(for maintaining weight), and give you a menu plan that is healthy. It also shows you the nutrients you are getting for the day. I use it for the recipes rather than the plan, but it would have been a great help when I was just beginning.