I don't own a plasma but I've read that the first little while you have to be more careful in what you watch. Over at the AVS forum they even run break in programs for their Plasmas but others say it isn't necessary.
A good idea is to do some kind of calibration. If you don't have a calibration disc look up your model for some reviews, they often have some suggestions for your set up.
Avs forum can also help you out in this way.
http://www.avsforum.com/avs-vb/forumdisplay.php?f=167