Another thning to do once a year or every 6 months is to "spring clean" your PS2. Older big models attract dust through the base vents & using a PC vacuum (not a house hold one as they are too powerful & could cause damage) give it a cosmetic clean & then using a micro fibre duster clean the CD tray of any dust then use a CD/DVD disc/lens clean in the way Lyndon above explained. I wouldn't touch the internal CD/DVD lens pot unless you actually know what your cleaning & how to clean it, the CD/DVD lens cleaner does the job just as well. Please always use the supplied cleaning fluid with the cleaning disc & not to use household or industrial chemical cleaners as they are far too powerful even when diluted

Sometimes the older PS2 has had problems reading Blue PS2 discs and a simple reemedy was to turn your PS2 onto it's side so it's standing up and vice-versa if it's happening the other way.