When you first arrive at the Cozumel airport, you will be directed through the customs process. Most airlines are good about making sure you have the correct forms.
Please note that upon exiting the customs area you will be bombarded by tons of people in white shirts and navy blue pants/skirts. And they will all tell you that they can help you with transportation, or offer to give you a car cheap, or get you to your hotel cheap IF you will just talk to them for a few minutes.
These are time share/vacation package sales people. If you are interested in buying one, then you might want to talk to them for a bit. If you are not interested, just head right outside of the airport and ignore them.
Once you walk out of the airport, you will typically be asked by one of the Taxi Van coordinators what hotel you are staying at. They will group you into vans and take you to where you need to go.