There will be several different things to vote on in the Caucuses. The two most important are the "straw poll" where you will vote on which candidate you support, and the "delegate election" where you will vote to elect people as delegates to cast the real votes for the primary. It's very important that you vote on BOTH of these separate votes. Don't just vote in the straw poll and then leave.
Straw poll: is an unofficial measure of who had the most supporters at the caucus. This is what is reported immediately to the media and it's important because this is what the media will use to report the "winners of the Iowa Caucuses. By winning this, Ron Paul can be shown as a serious and viable candidate.
Delegate Elections: This is the one that isn't publicized as much, but actually officially counts toward who gets Iowa's votes for the primary. You'll be voting on people to be DELEGATES, not for the acutal candidates themselves. It's important that you find out which potential delegates will vote for Ron Paul and vote them all in. To find this out contact HQ or your local meetup.
In the past, people have voted in the straw poll, then left the caucus before the delegate vote thinking that they had already done their part. The result is that their candidate didn't really get credit for their votes.