Number ONE mistake (can't even call it a mistake though) people make with cleaning their pool is......
They vacuum too fast, unless you move your vac head about 1" per 3-5 seconds, you WILL end up with a "new" pile of dirt, actually it's an OLD pile of dirt.
When you vac your pool, you stir up the settled debris, this debris mixes in the surrounding water and "DISAPPEARS", but unbeknownst to you, it's not getting sucked up and filtered. Once you're done, you sit back and say to yourself "WOW, what a clean pool!", what you don't know is that there is a ton of dirt currently suspended in the water, but the particles are so small you can't see it until it settles in bunches - voila - your dirty pool the next day.
Nothing you can do about it other that go REALLY slow, and that will extend your vacuuming from 1 hour to 5 hours - your choice!