I really like CanadianDiver's suggestions! I'll also recommend Vance Harlow's regulator overhaul book "Scuba Regulator Maintenance and Repair" http://www.airspeedpress.com/newregbook.html when you're ready for that, and for beginners The Certified Diver's Handbook http://www.amazon.com/The-Certified-Divers-Handbook-Underwater/dp/0071414606 is a collection of a lot of little tips that help you become a more proficient diver- it's a light read but very informative if you're just starting out.