Catherine,
After you disembark the plane, you will come down into the Immigration Hall. Take a moment to work out where the lines are forming and stay away from those areas - most people tend to form queues in the middle of the hall and those stations to the far right or left often have little or no queues. Make sure you have filled in your Immigration and Customs forms correctly - if you've made a mess of it, you will be sent to the back of the queue.
Once you have cleared Immigration you will need to collect your bags from the carousels just beyond the Immigration desks. You then clear Customs - usually just a walk through. As you exit this area, you have to give up your bags which will be transported to the main terminal. It's then up the escalator and you'll pass through a security area.
Upon exiting security, bear left towards the tram which will take you over to the main terminal to be reunited with your luggage. Walk to the far end of the waiting area - this way you will be first off at the other end. The trams come along every few minutes.
At the other end, bear left again and down the escalator to level B (baggage claim) and right at the bottom of the escalator towards the Virgin conveyors for second baggage reclaim. I normally wait here for the bags (I always beat them over), whilst dh takes the elevator directly behind down to level A and the car hire desks. You will then need to go to either the dedicated Virgin Dollar desk, or the regular Dollar desk, depending on whether or not you have booked a package with Virgin. You can't miss either. The times we have booked fly-drives with Virgin (and so have been using the dedicated desk) dh has been there so quickly, they have not been ready for him - you will almost certainly be the first there. If you are using the regular Dollar desk, then you will be in line with anyone else renting from Dollar (from any flight), but dh has never had more than a couple of people waiting ahead of him. Sometimes he has finished before I've turned up with the bags. On more than one occasion we have been away from the airport within half an hour of touching down. Usually it's 45 minutes to an hour.