As long as you remove the burrs and any dirt from the PVC pipes you don't have to sand the PVC pipe to glue them together.
I however always have sanded the PVC pipe because I use sand paper to remove the burrs off the ends of the PVC pipe after cutting it anyway.
So it doesn't take that much more effort to just sand the PVC pipe before gluing the pipe together.
After you sand the PVC pipe and add the glue you then should twist the fitting or pipes back and forth a few times and then hold the pipes and fittings together for at least 1 minute.
Then allow the PVC pipe to cure the glue for at least 2 hours before turning the water back on.
Some people have turned the water back on after 15 to 30 minutes but I like to wait at least 2 hours for the full cure time.