Me: I siphon the very top. Basically at full strength, siphoning detritus/cyano/algae off the top.
Really only done as needed, when it is not looking so great.
It also commonly removes a bit of sand as well, which I wash and replace.
I tend not to disturb the sand bed much beyond that.
As to that being best - really hard to say.
I am rather curious as to other opinions as well.