I’m a firm believer that a plant-based diet is the healthiest of all diets out there, but you still need to be informed about nutrition because when you eliminate all animal products, there are some vitamins and minerals that just don’t exist through an animal-free diet. The biggest one is B12. If you aren’t eating any animal products, you gotta make sure you are getting your B12 through a supplement or nutritional yeast.
Here is a post from Smart Diet that discusses what supplements you might need if you are a vegetarian or vegan.
Do Vegetarians Need to Take Supplements?