At 9:
You run more than most back players, if not the most on the pitch as you have to be at just about every breakdown in play. So endurance is huge!
To build your accuracy i reccomend taking a ball standing 5m from a pole and just passing to the pole off each hand 20 times, see how many times you can hit, then keep adding distance as you feel more and more comfortable with your accuracy.
To build pass strength i would reccomend using a medicine ball and do several types of explosive movements with those, such as side throws and stand back to back with a partner and pass the ball between you. This site has some good excersizes for rotational power:
http://www.t-nation.com/findArticle.do?article=199torn2
From there its all about just working on your ball skills and kicking skills, off both feet and both hands. Try to pass a ball as much as possible.
Tips i can give you are always be on the lookout for penalties at the breakdown, as tehmite said dawes and gregan pointed it out to the refs all the time, i do it as well and it works really well. IF you see something illegal goin on ***** and moan about it, but don't expect to always get the call and be ready to play on. Also look for small gaps on either side of the ruck, from personal experience it seems easier to find them on the blindside. And the last thing i should say is work on your cooperation with your fly half. He is one of the vital links in how well you function, and having good communication and good chemistry with him will make the team click that much better. Work with him to get his timing down so you know how and where to give him the ball.