Listen to the music... A LOT. Know it inside & out, backwards & forwards. Listen to it til I practically can't stand hearing it any more. Run through it a couple of times & videotape yourself dancing to it, if possible. Then play it back for yourself to see what works from the audience standpoint & what doesn't. Practice IN YOUR COSTUME a couple of times before your performance (this includes hair & makeup).

What she said. Any time I'm playing on the computer, doing dishes, general housework, driving, etc, I'm listening to the song. I also dance to it as much as possible. You'll find that certain parts of the song will call to you to do a certain move.
And definately practice with the costume if it's new or if you're going to do something different with your hair. I don't practice in costumes I've worn several times cause I'm use to them.
I'm so glad I practiced in my cabaret costume before I wore it for the first time. During practice, I found out that the skirt likes to slide up and the front of the skirt likes to slide down. So I was able to safety pin the skirt to a pair of shorts and my costume stayed put during the entire performance. :-D

Another example: I wore a hair piece for the first time during a performance. Bad idea. I planned the end of the song to have about 4 quick spins. Luckily, you couldn't tell in the video but my hair had come undone. If it had been any earlier in the song, it probably would have fallen out. Yikes! Hair flying everywhere! lol

The idea is to know the music, practice in your cossie, have a plan...But none of that for me! I do listen to the music lots but I don't really "practice" for solos unless it's just to see if something I see in the music is going to work physically.

I guess I'm a bad example.

I can second (or third, whatever) other folks' suggestions for becoming very familiar with the music and listening to it _a lot_. Another thing I would suggest is to become extra familiar with the beginning of the piece of music and how it ends, and maybe having a few scenarios worked out in your head on how you would start and end the dance.

Additionally, it can help to try out different moves or combos to see if they fit with the rhythm/music. Have fun!!

I may or may not be doing a solo improv piece this weekend, to live music, so I had better take my own advice!