Do you clean your records before play, after play, or once (and then never again)?

I only clean them if I spot contamination between grooves. That includes fingerprints. Wherever the fingerprint is the dust gets stuck and can't get airborn out of play surface. Otherwise I use carbon fiber brush before each playback with no professional RCM usage.
I have records in my collection I didn't clean for over 20 years and they still don't need cleaning.

This is not the case what you don't see won't bother you. Record may look just fine when in fact it is very dirty.
Yeah, it amazes me too that some don't pay attention to proper record cleaning. But cleaning before each play is probably too much, won't hurt though.

Interesting method Mapman - I always go perpendicular but I will try you method next time.

@inna 
Frequent cleaning can destroy smoothness of pressing in other words wax so it WOULD hurt. Cleaning should be as necessary. To me the best sign of cleaning is change to noisier playback or stylus contamination after going with just carbon fiber brush. Other than that, if stylus is clean after playback AND playback is clean, than no need no matter how long.

pops worth noting I also tend to rotate counterclockwise somewhat further while moving brush outward to help traps dust. Its a technique to hone a bit once tried. Main thing is end of brush is always extended beyond the perimeter of the record, with brush probably never rotated more than 20-30 degrees counterclockwise  max.