1. Impatience and self entitlement
If you date is rude to waiter, or is constantly impatient waiting for his food and is simply a jerk... then that is a clear sign.
2. No interest in you
If you feel like you are interviewing him, and that he doesn't fire questions back at you to get to know you- sure sign.
3. Critiques everything
If he/she is already critiquing everything around them, including the poor quality of food, and what the woman at the next table wore, and her lack of style... you probably got yourself a narcissist.