TURN DOWN YOUR CONTRAST!!!
for the first 300 hours of your plasma, you should watch is VERY DARK!!!
this will avoid that retention. also, use whatever your TV has built in to avoid the burn in effect. some TV pictures actually shake (not noticable to the naked eye), and will help avoid burn in. also find a channel with white noise and let it play for 20 minutes or so...
i pooped my clothes when my brand new 50 in plasma had burn in, but after some research, i did these and it went away, and with the contrast turned down, did not return...
after the first 300 hours, you can set it to normal settings and avoid burn in or residue unless you leave a still image on for about 6-10 hrs.