1) Manners: Don't walk into any potential work place walk up to the counter and say, "Hey YO! Are you hiring? Here's my resume!" and walk away. Yes, this has happened a number of times to me.
2) Professionalism: If you're going to apply to any workplace before stepping inside ask yourself if you are dressed appropriately. If they wear a uniform chances are whatever you have on is fine. If not, gear your outfit to look like you fit in. If you don't want to do this because it's "not you" then dont get mad when you dont get a call back.
3) Spell check: Too many times have I seen resumes with incorrect spelling. Sure the computer can check spelling, but it doesn't check grammar! It's a small thing in the road of life but it builds a stronger foundation for you to get to where you want to go. Their, there and they're do not mean the same thing even if they sound the same.