I agree with Mick, (surprise surprise).. the Stefan Hannigan, book and tape are a great way to learn, (the videos are good too)... the only thing I disagree with is the suggestion that you buy an 18 inch one..... it depends on how big you are..... I think the 16 inch ones are more comfortable to play......Big Mick has a HUGE bodhran (22 inches Mick?)... but that is a good size for a big man like him... but I couldn't play one that size.......
basically what I'm saying is find one that's comfy for you..... it should be able to fit partially under your arm in comfort....
slainte
alison