If you haven't started running yet ask yourself, "why not?". While Cross Country is something you may be able to just show up and do, after all it's just putting one foot in front of the other, your success and the teams success weighs heavily on the work you put in prior to the start of the season. Can you imagine taking a vacation, going to a special event, or showing up to school and the person in charge decided to not prepare and just see what happened? I would bet there would be chaos and disappointment. While the circumstance is different, the idea of getting ready for something is the same. If you want to have a good time, do your best, and improve then you should take charge of what you can. Go outside and run.
Seasoned runners with a few old pairs of running shoes:
At this point in the pre-season you should be covering 3-4 miles 4 times per week (or running 25-35 minutes). This is your base building. Add points of speed work here and there by picking targets to accelerate to briefly then slowing back down again.
Rookies:
It is my hope that you are building up to running two miles without having to stop. Take small steps toward this. Try running for 3 minutes and walking for 2. Go at this rate for 20-30 minutes or for 2-3 miles. Maybe you can run a mile now but can't quite make it to two. Jog your mile then walk for 5 minutes and try to run another half mile before your next break then do another half. It's all about progress so push yourself.