I'm with MPPL and HPS and it's definitely fun.
The stages that MPPL designs is a little more catered to new folks, as it doesn't involve a whole lot of movement. HPS usually designs stages w/ a lot of movement, most times you running back and forth on more then one occasion. As b2b said, take it slow. If you attempt to go at near the speed, or even half that of the more seasoned shooters, your will do horribly. Also be vary wary of your muzzle sweeping. It's an honest mistake from most people, but a mistake none the less.
As far as practice goes, there isn't a lot where you can. The most you can do is practice your draw and reloads at home, and a lot of dry firing. As far as live fire, you more or less have to remember what you did the last match, and attempt to change it, or try a different approach. There's a lot of videos on you tube, both locally and nationally. Watching those gives you a good idea of the different styles people have, as well as giving you somewhat of an idea of what to expect.