Welcome to the party!
It's a slow time of year for fantasy football, but the best thing you can do in the offseason is learn the players on all 32 NFL teams. Learn the depth charts and watch for football news throughout free agency and the NFL draft for trades and depth chart changes.
Knowledge is power -- and with Al Gore's invention, there's never been a better time to pick up this Fantasy Football hobby (obsession). If you have questions, ask them on the appropriate forum here at the Cafe and you will usually get solid advice.
As we get closer to the start of the NFL season, you will want to fill out your draft board with rankings for each player. You will also want to do some mock drafting... there are several sites (I like mockdraftcentral.com) that will allow you to practice drafting. It gives you an idea of what to expect when it comes time to do your own draft.
The last and most important piece of advice is to have fun. If you are drafting and have 2 players ranked closely together, don't hesitate to draft the player you like better, even if it goes against "conventional wisdom".... remember, it's you that has to watch (and cheer) for your roster during the season... I find it more fun when I have a few of my favorite players on my roster.