I've given a lot of tailwheel instruction and it's truly my favorite type of instruction to give. I think I had a few hundred hours of tailwheel time before I started instructing.
Step one for you is to get the endorsement and see how it fits you. Read all that you can from reputable sources on tailwheel technique. The key word there is REPUTABLE. I recommend
Plourde's The Compleat Taildragger Pilot and
Imeson's Taildragger Tactics. Both of those volumes are phenomenal references and will really help you acquire an understanding of the physics involved as well as some potentially life (and airplane) saving techniques. Find the most experienced tailwheel instructor you can and pay him what he wants. Take copious notes and don't be in a rush and you'll be fine. Study can only make up for so much experience though.
I was fortunate enough to start flying taildraggers for a commercial glider operation with only the endorsement. It was there that I gained the experience that I felt was necessary to instruct and mentor beginning taildragger pilots. I had a few harrowing moments at the controls that I was able to relay to my students and call upon to correct their mistakes. Had I seen those situations for the first time while giving dual in the back seat of a Citabria, I may not have had the time or expertise to make the right call. I will advise you to get as much practical experience as you possibly can. Environmental conditions play a huge factor in the successful outcome of your flight.
In the end, it's all based upon your comfort level. Don't listen to anybody who tells you that you should have a certain magical number of hours tailwheel before you start instructing. Before you start taking students do a thorough, honest analysis of your skills and knowledge and determine if you have what it takes. Once you sign off that student his life is in your hands.