If I am a vegatarian, what should I do to make sure myself for positive protein balance?

Vegetarian protein. The vegetarian diet can be healthy. The recommended amount of protein is about 55 g for a 150 lb person. See:http://www.cdc.gov/nutrition/everyone/basics/protein.html for more information.
Review protein requirements. Protein amount dependent upon various factors, age, sex,activity level. Few vegetarians are deficient in protein, especially if eating lentils, tofu, milk products. Need to ensure sufficient B12 intake which is not made by body and not usually in vegetables. Check CDC and Registered Dieticians website for amount of protein recommended for your body.