I'll say something like... 'sorry, i didn't get that' or 'could you say that again?' or 'there's too much noise, I can't hear', depending on the situation.
If it's important- I've found ways of paraphrasing what I think I heard correctly and say that to them and ask them to fill in what I missed.
Edit: I should add that I don't have much contact with people... Other than my hubby, I only really speak to a couple Moms in my Moms group when we have playdates, my son's OT and his speech therpist. Sadly, for the speech therapist I've tried to get her to write things down for me, but she doesn't get that I just don't understand some of the stuff she says to me. She uses "Motherese" when talking to my son, and seems to mumble with me. 
Last edited by BeautyWithin on 26 Feb 2007, 6:05 pm, edited 1 time in total.