When looking in from outside, I think many atheists see us wacky Christians talking about 'hearing God' and are pretty sure we're either:
a) Barking mad and dangerous.
b) Gently self-deluding.
c) Inclined to invent stuff that gives us permission to do what we want.
d) Trying to fit in the the rest of these odd people.
So I don't want to talk about the mechanics of hearing especially, other than to say that various (strong Christian) people have come to me independently all saying the same thing - it makes you start to take note when you hear that, especially when they aren't necessarily even doing it to help you.
But regardless. :-)
This morning I was sat at breakfast, just reading the bible as usual, and it seemed to me the Spirit said "you need to make some notes about this and that, because the man who was due to preach may not be there this morning". And that's how it turned out. So today I actually spent less time in preparation than I did speaking, and I felt far happier about what was said and the response it produced than last week when hours were spent in preparation.