1. You go out of your way to be nice to people you wouldn't normally befriend.
2. You remember small details about people, and they always like you more as a result.
3. You know that sometimes you have to just smile and nod when people treat you badly. (And that doesn't mean those people are right.)
4. You always carry a writing utensil so you can write things down.
5. You actually pay attention when people talk to you.
6. You're willing to do favors for people.
Sometimes, you'll be in a position to do something for someone that's easy for you, but would be hella difficult for them. Take the chance to make their lives easier, because you never know when the position might be reversed.
We're all in this together, especially when "this" is a horrible dinnertime shift when half the wait staff has called in sick with turtle flu, and the stove decided it was all done with functioning.
7. You don't sweat the small stuff.
8. You know that a sincere apology goes a lot further than you think it will.
9. You know that there's a time and place for personal problems.
10. You know not the judge people by their appearance.
11. You know that manners make a big difference.
If there's one thing you learn in a service job, it's that some people are very rude. Those people can easily put everyone in a terrible mood.
Bottom line: Be aware that you're in public, and you're a grown-up. This is not to say that you have to open everyone's door, but it doesn't hurt to add in that little extra effort. You never know, it just might make their day.