How to gain agility?

I guess the title says it all, but what is a good way to gain agility. I know that when I begin to go to classes I will need to be agile to accomplish some things to their full potential and grace. What are some things I can do to gain agility? Like push-ups make you stronger, what makes you more agile?

Practice! Your instructor will show you what to work on in the particular school you end up training in. No need to worry about it until you start training.

Yes like Matt said, ask your instructor what particular exercises will help in your martial arts training.
However, a good way to gain agility are ladder drills and suicides.

Like they both said, and i suggest splits, flexibility can help you agility, trust me, it can make a big difference, but yea practice makes perfect, good luck.

multi-kicks with both legs without support is also a good way, plus jumping jacks. Ballet or dance are also good ways to increase agility. Basically anything that keeps you moving and off balance will do.