How often, and how, do you clean your stylus?

I cut a round piece of Magic Eraser (lots of praise for this product used for this purpose) to fit into the cavity of a trimmed rubber furniture foot, which then sits on my turntable plinth between platter and tone arm rest. I lower the stylus onto the Magic Eraser as I'm cleaning the vinyl with an Oracle brush. Do this every side. Stylus is always perfectly clean, and the procedure takes no effort whatsoever, nor does it risk harm to stylus or cantilever. 

I do similar as @snilf only with the Japanese Onzow device on a little purpose-built riser. Volume on, to listen for contact.

Seconding @mijostyn ‘s concern for blue tack. There’s also a greasy component to that stuff (why you should also never use blue tack on paper / posters you plan to re-use or keep in clean shape) and I’m not sure whether that would affect the stylus (whether for better or worse).

I clean only when it sounds like it needs it. Couple of times a year with many hours of playing in between. With this hobby, I don't look, or listen, for problems that aren't there. 

That's a very personal and inappropriate question. For shame!

As it is not mentioned, I will add it to the items that can be used to remove particulate from a Styli.

The product is Jewellers Putty, used to pick practical of Gem Stones.

Making a Match Type tool using a Tooth Pick will allow for it to be used as a probe, or a small ball to lower the Styli onto are both OK methods.

If a TA has a Cue Lift Lever, and the Volume is not turned down, the Styli can be lowered to just above the Groove, prior to it making full contact, this will show immediately if a particulate is present that will effect the sound to be produced.

If all is quiet above the Groove 99% of the replays will be quiet when making first contact with the Groove.

The isn't too many options to use as a safeguard to particulate collecting at the styli throughout the replay.