If you have an idea, and you write it out, but you don't like how it reads, what are some methods for rewriting it so it sounds better or more appropriate or even just solid?
Practice speaking it aloud in a variety of ways, and whichever sounds more natrual, not fundamentally better but, natrual is the one you want.
When I have this problem I try to strip away everything until I get down to the basics. Try making the sentences with the key words you need to convey your idea. Then yo can work your way back up, making it more complex until it feels right. What Steak-Ums said is very good advice.
It all depends on what about it doesn't sound right. Maybe it's as simple as needing a better verb choice, or it may be a muddled mixture of ideas that don't belong in a single sentence. It could be too much description in an action sentence that needs brevity, or it could be a stripped down sentence where the narrative needs more description to bring it to lif. So the first step has to be, analyze why it doesn't sound right.
I think Cogito brings up a very good point. It's really impossible to tell you how to rephrase it. Rather, you should focus on why it doesn't sound right and go from there. However, if we're talking specifically about dialogue, try to make the dialogue fit the character more.
I have this problem quite often. I actually re-edit it atleasy five or six times before I get it the way I want it. Just try and say it aloud like some people already said and continue your story after the third try. Then, once you have the phrase out of your mind, go back to it and see how it sounds like now. It might sound normal after that ammount of time not thinking about it. Sometimes, you might even have to do that about ten times.
Dialogue is an entirely separate can of worms. Good dialogue needs to reflect the character's voice, but not record everything that would come out of the character's mouth. Dialogue is strategic, and should expose information to the reader, not just be there to fill space. Small talk has no place, unless it exposes something at another level.