Don't forget about or neglect the suspension on your tandem. Regardless of brand, pull those forks apart, clean or replace the seals and wipers, change at a minimum the bath fluid if applicable, and also replace damper fluid if needed.

On the other end, if you ride a Thudbuster, make sure the bushing are not worn, pull that post apart and lube the elastomers and bushings. If you have a rear shock, might be a good time for a full service, at a minimum, clean and lube the air sleeve and seals. While apart, ensure the shock has plenty of resistance to compression indicating the nitrogen charge has not leaked out. If you run a coil-over, give a good look at the spring seats to ensure no cracks are present. Never hurts to remove the spring and verify ample nitrogen pressure.

Obviously, this is on top of you complete teardown and rebuild of the entire bike including pivots in preparation for a solid year of 2013 riding.