Summarize this article:

A red flag is anything that could be a potential problem in the future. It’s easy to get caught up in the romance, but it might be best to take a step back and evaluate the person you are seeing for who they really are. Try thinking about all of the things that you know about them, and make note of anything that is questionable.  If he says he’s not ready for commitment, and that is something you are looking for, you should believe him and not try to change his mind. Red flags can also be things like a short temper, tumultuous relationships in his past, or indications of a substance abuse problem. Since you’re looking for a strong relationship, you should take your time getting to know them. The longer you spend with them, the better an idea you will have of who they really are. Don’t feel like you need to rush into something just because it feels good. One of the most exciting and fun parts of dating is getting to experience new things together. Pay attention to how your partner reacts to different situations and ask yourself if you’re comfortable with the way they handle different stressors or uncomfortable environments. For example, holidays are sometimes very high-stress situations and environments for people. How your partner acts in this environment might be a sign of how they’ll react in other high-stress situations. If you begin to feel uncomfortable, uneasy, or afraid in your relationship, don’t be afraid to leave immediately. Your partner should never threaten, hurt, or ignore you. Confide in someone you trust and cut all ties with anyone who is unhealthy for your mental and physical health.

Summary:
Look for and notice red flags. Take your time getting to know him. Spend time with him in a variety of environments. Say “no” when you need to.