Playing centre is a very demanding position as you need both the stamina of a runner and the defence of a prop. at this position your pace is vital, you need to exploit gaps and be able to produce good offloads for supporting players. you also need to be physically strong as when there are no gaps in the defense wall you need to be able to take the ball and smash through the opposing teams defense wall. just make sure that you keep your eye on the ball and on your supporting players and when you have the ball if you see and opportunity take it but if you are going to offload make sure that the ball is not slow :) hope this helps and good luck :)
Every 12 has their own style of playing, there is no right or wrong way to play. However, Sonny Bill Williams (Chiefs and New Zealand) was absolutely incredible in 2012. I strongly suggest you watch some of his videos when he was plying for the Chiefs and see what he does.
