Turn off the sink's water supply.
Cut the caulk seal around the sink with a utility knife.
Remove everything you have stored in the cabinets beneath the sink. Place a small plastic container underneath the sink's P-trap.
Loosen the nut connecting the P-trap to the sink's drainpipe. Loosen the nut connecting the P-trap to the exit pipe.
Remove the P-trap. Any excess water left in the sink's drainpipe or the P-trap should fall into your plastic container.
Look underneath the sink for sink clamps. Unscrew and remove any sink clamps you see.
Push the sink base upward from underneath the sink. This unseats the sink. Lift the sink away from the vanity.