I just mean in the same way that they are (or should be) nice, friendly and charming with their friends and family.
If you meet new people and you find them attractive, treat them like they are already a friend that you've known for years. Don't be weird, just tell them a funny story, embarrass yourself, show them that you're fun and human. Those are my rules, and I've dated way out of my league my entire life. I'm not saying it's easy, but it is simple (not to be confused).