do a favor

Related to do a favor: stick with, run by, let off, in turn

do (someone or oneself) a favor

1. To help someone else, typically at their request. Sometimes used sarcastically. Hey, do me a favor and take these bags into the kitchen while I get the others from the car.
2. To do something to help or better oneself. In this usage, a reflexive pronoun is used between "do" and "a." Do yourself a favor and go to college—now that I'm older, I regret not having that experience. Because I knew that I had to get up at 4 AM today, I did myself a favor and went to bed early last night.
3. A request for someone to stop doing something bothersome or annoying. Can you please do me a favor and take your loud music somewhere else? I'm trying to sleep! Look, I know you want to help, but do us a favor and just stay out of our way.
4. A response to a statement that the speaker finds ridiculous or stupid. ("Favor" is usually spelled "favour" in British and Australian English.) Primarily heard in UK, Australia. A: "Katie seems nice." B: "Oh, do me a favour—she's one of the cattiest girls in school!"
See also: favor
Farlex Dictionary of Idioms.

do someone a favor

 and do someone a good turn
to perform a helpful service to someone. Would you please do me a favor and take this letter to the post office? My neighbor did me a good turn by lending me his car.
See also: favor
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • (Is) that everything?
  • (I) would if I could
  • take (something) under consideration
  • a bundle of fun
  • advisement
  • take under advisement
  • take (something) under advisement
  • (well,) I never!
  • couldn't happen to a nicer (person)
  • twenty-twenty hindsight, with