i do it every other oil change... or every six months...
i hit it on my garage wall to knock the dust loose...
then i spray it inside, then outside with the soap...
then i wash it with warm water...
then i let it sit overnight...
while it dries, I take off my intake plumbing, wash it wish dish soap and warm water, dry it, and polish it (chrome.)...
then i clean the MAF and IAT sensor with MAF cleaner...
then i clean the MOUTH of the throttle body with TB cleaner (nothing past the butterfly.)...
then i reassemble the piping, put on my extra air-filter (yes i have two of them,) and then re-polish the chrome...
then the next day i apply the filter oil and let it sit over night again...
the next day i put the freshly cleaned filter in a plastic bag, into my cabinent full of auto maintance stuff...
i then take out my MAF and IAT sensor and wash them both again with MAF cleaner and re-assemble...
my anal and detail oriented intake-cleaning is now complete
(and no, not very many people are as anal as i am. lol)