You need to read up on how to cycle a tank before getting any fish. Or do a fish in cycle. There are instructions on here. Just check out the articles section.
As for cleaning a sand substrate, I started out with the usual syphon type vacuum. It works okay. I had better luck with the smaller diameter tubing ones. Somewhere in between the normal air line tubing and half inch diameter tubing. The larger tubing sucked up too much sand. I know use one of those battery vacuums. It has a bag that the stuff you suction out goes into. It does suck up some sand. I just empty the bag into a bucket and rinse the sand that was picked up until clean, drain it and dump the sand back into the tank. The battery one makes it easy to clean up between water changes. You can also use it to syphon water out of and into the tank. This link shows the one like I bought. I got it cheaper though through another vendors.
Amazon.com: Vktech Aquarium Cleaner Fish Tank Vacuum Gravel Filter Cleaner: Pet Supplies