Ive had baitcasters for a few years now, but have never really performed any maintenace on them.  Except to oil all the moving parts on the outside..  What exactly do I need to do to keep my reels in good working condition?  The majority of my reels are Diawa.

Tear them down once a year and clean out the old oil and grease and relube. You really should have a professional due this , it will save you money in the long run.

Go to Reel Mechanics website.