Dear SuavePlayer,
You are smart to recognise your problem I only became aware that I slouched when I took up Dancing.....I found the best thing is to be aware that you have a problem,little stick on discs about three eighths of an inch diameter,will help,stick them at key points at home at work,your car,this will encourage you to straighten up.....Stand in doorways heels to the bottom of the side frame,bum,hips and back of head all touching as well flatten yourself and hold for a number of times increasing time every few days....I found chin ups and pull downs were very helpful too.