Slides are probably one of the most important improvements made to recreational vehicles in a long time. They come in manual, electric and hydraulic. Each requires is own form of maintenance.
With all slides there are some common maintenance tasks. First never store anything on top of the slides whether they are in or out. Second, make sure the top of the slides are clear of any debris before opening or closing the slides. Debris can tear up the rubber seals causing leaks and eventual replacement. Make sure that all drawers, cabinet doors and chairs are properly stored.
Manual Slides are probably the easiest to maintain. A simple lubrication once a year with a good quality silicone spray will keep them working for years to come. While you are at it, clean and treat the seals with a rubber seal spray.
Electric and hydraulic controlled slides should be lubricated annually using a quality silicone spray and the seals cleaned with a good rubber cleaning spray. In addition, you want to make sure the batteries are in good working order. Clean the connections at least once a year. Check under the slide for signs of rubbing. Keep the slide tracks, equalizer gears clean and properly lubed. If the slide is going to be extended for a long period of time, a slight coating of hydraulic oil will help prevent the ram from rusting. It is a good idea to exercise the slides at least once a month to keep the parts working properly.
Check the connections of the ram to the slides to ensure the bolts are tight and adjusted properly. There are numerous methods for adjusting the slides. Normally the top of the slide will contact the side of the rv first and then the drive will pull the bottom tight. If the operation is out of whack you will need to perform the proper adjustment procedure or contact your rv repairman.