How to Repair a Sliding Door — suggests checking tracks for debris and cleaning. Look for dents and dings. Put some graphite onto rollers. Use parrafin wax on tracks. If door continues to stick, glass company can replace nylon rollers for about $60.

How to Unstick a Sliding Glass Door — suggests cleaning and lubricating top and bottom tracks if they show signs of wear. Using a butter knife or screwdriver to push down the top rollers will usually help to remove the door. (Use caution and have someone there to help you as the door can get heavy.) Use toothbrush to clean tracks. (I also use papertowels and hose attachment on vacuum.) Dry tracks thoroughly with blow dryer (or allow to air dry). Check rollers for wear. If cracked or flat spots, replace them. Use household oil or graphite to lubricate tracks (candle can also work, but is more temporary). Look for bends in track where door may be catching. Look to see if frame is out of alignment due to house settling.

Easy Slider — suggests regular vacuuming of tracks, but says to NEVER lubricate as it will attract dirt. There is a screw on the edge of the bottom rail of the door that can be turned a few times to adjust sliding glass door. When checking alignment, stand back and look at door from outside and you should see a uniform gap along bottom and top of door. See article for what to do if too high or too low.