I usually let my water sit for 24 hours, just because the water temperature that comes out of my tap fluctuates wildly. It will be freezing cold one second, then scorching hot the next and the slightest adjustment can actually make it worse. Letting it sit that long allows me to have it a stable temp before I put it in the tank.
As far as vacuuming, I don't have on yet, I use a turkey baster. It's kind of hard to use in a 5 gallon tank, but I have a minbow, so it's kind of narrow and a regular size vacuum is way too huge for my tank. I am going to get a small one, but I have to save up the money for it. (I'm a teacher who got laid off due to budge cuts and am working very sporadically and every little bit of money goes to food for my family)