I've personally never performed a lens cleaning on any of my CD/DVD/BD/HD-DVD drives/players. I do make sure that the disc's are always clean before putting them in though. Also, if a particular disc is having issues, look at it in the reflected sunlight. Does it have fingerprints all over it, possibly some scratches as well from kids handling it
First thing I do is take it to the sink, wet it down a little, but a dab of liquid hand soap (nothing with any grit as you don't want to add more scratches) rub it across the surface, rinse it off, shake the water off, you can towel dry the back side but not the front unless you have some lint free towels available. You can wave it around in the air a bit to dry.
Try this, if this didn't work and it's scratched up some (but other disc's are playing fine) then you may consider getting a disc repair kit to resurface the disc's. I had to do this to several of my son's Wii games due to poor handling of the games. I love BD's for this because they are very hard to unintentionally scratch, never had a PS3 game scratched or BluRay movie damaged.
If it's one or two that aren't playing and they do show signs of scratching, I'd try the disc repair route first. Only if that fails would I bother with a lens cleaner.