Have you ever heard the saying, "How do you get to Carnagie Hall? ... Practice, practice, practice."  If you want to get better at something (like paintball), you have to practice.  So like anything else, if you want to get good at paintball, you have to practice; but where?  My team (Team Trinity) has found a small, but very nice piece of woods close to where we all live to play in.  We have a designated playing field with a multitude of cover, and obstacles.  We've also set up a target field with three targets strategically placed by trees to simulate an opposing player taking cover.  This helps us practice aiming, rolling maneuvers and different moves we come up with.  There are many drills one could do to practice, but you just need a place to do it.  If you don't have access to woods or someone's property, you can also practice at a commercial field but this could get very expensive depending on how often you want to practice.  Just remember... the more you practice, the better you'll get!  Your best bet though is if you can find a nice piece of woods or a field nearby and use it to practice with your team. 
Matt Kresch, Team Trinity