I try to keep my carry gun clean, but the main USPSA gun gets cleaned 1-2x yearly, usually including sometime within a month before the section match in the summer. Occasionally it'll get cleaned "off schedule" if I find that it's gotten exceptionally filthy, but that's pretty rare. As for how I do it, given that I usually wait until it's gotten pretty dirty, I usually hose the frame out with an extended shot or two of the Hornady One Shot aerosol cleaner over a waiting pile of paper towels. The gray sludge that runs out of the guts of the gun is not to be trifled with.
As for cleaning the barrel, slide, etc, I usually do that with Liberty Lubricants products; I got some solvent and CLP for free via a promotion, but I like how it works well enough that I'll be buying more when I eventually run out.
Like others, I used to clean more often, but I eventually came to the realization that the only purpose that truly served was to raise my level of chemical exposure. Given that, I gave myself permission to be lazy about it and (probably) reap the rewards of being healthier over the long term.