I think you can tell a lot about a person from how they place their order at a restaurant. I think that it is pretty safe to say that probably about 75% of the people that say "Give me the …" or "I'll take the…" are people that I would not want to be around. My impression is that these people are usually self-centered.

People that say "May I please have…" have a better chance of being more like the people I want to be around.

You can also tell a lot about a person by how they talk to wait staff. People that bark out commands, or that don't end a request with "please", or that don't say "thank you" when something is brought to them are probably not my peeps either.