Even if you believe you've chosen vegetarian food in a normal restaurant, be sure to check on how the entrees are cooked -- getting true vegetarian meals in some restaurants can be tricky. For example, vegetables may be cooked in broth, or have tiny bits of meat added to enhance the flavor.
Be very careful when ordering what appear to be vegetarian dishes in a Mexican restaurant. Almost all refried beans are made with lard (animal fat) to add creaminess, and even something as innocuous as Spanish rice may be cooked in beef broth.