Going to break it down into off the field and on the field.
OFF THE FIELD
-Get a non-student advisor/manager
Class A is a multi-year process. It helps a ton to have a non-student who helps keep an eye on the long term goals from year to year. When you get to the point that your president just quit or the school cut your funding or who know what else, your advisor can help keep things running smoothly.
-Have as much depth as you can
Keeping 12 Class A players is about 3 times as hard as keeping 6 Class AA players. I don't know why but in my experience that's how it works. People drop, get their girlfriend's pregnant, crash their cars b/c of DUI's etc. Plus, the more people you have, the lower the per person cost.
-Spend lots of non-paintball time together
At Rutgers, when we started playing Class A I made it a point to have everyone eat together after we did our fitness work outs. As they say, "who you eat with becomes your family". Class A requires a lot of team work and the more you can build that off the field, the better it will be on the field.
-Get in shape
Even with 10 players, being in shape pays off big time in Class A if only because most teams don't make physical fitness a big part of their practice regimen. This is especailly true if you are down on points and need to win quick. Having extra gas in the tank in the second half can push things your way.
ON THE FIELD/PRACTICE
-Get a DEDICATED on field coach
I can't tell you how many times I've seen a good team lose because they're on field coach didn't know what they were doing by getting penalties, throwing the towel at the wrong time or just not having a trust balance between them and the players on the field. You need to practice with your. coach in Class A situations (e.g. two coaches, one player from each "side" in the snake) to build that trust over time.
-Class A is way harder than AA
Go back in the schedule results threads and you will see Top 5 Nationally ranked Class AA teams join Class A and they don't win a game all season. As already mentioned, the pace is faster, the format punishes mistakes quickly and little things add up fast. A good rule of them is that mid-level D3 PSP Race-To teams are roughly what you will be facing in Class A.
-MORE SPECIFIC TACTICAL ADVICE
I highly suggest you read the articles I've been posting about college paintball stats as those have a lot of good info (they're based on Class A matches). The article on when to throw the towel is probably the most useful to new teams.
Here is the link:
http://www.pbnation.com/showthread.php?t=3882621