First answer is obvious...climb.
Second answer is easy...climb some more...outdoors if possible.
Past that I don't know if I have ever figured out if one should take a climbing specific training regiment, or pick up something elsewhere like yoga, running, weight lifting, or a combo of everything.
I ask myself that question because I recently decided to give crossfit a try, thinking that the whole body aspect of it in concert with the cardiovascular benefits could really up my climbing game. Of course I'll keep climbing, but as someone who has led a life of fitness through sport I need a change in my routine.
Need may be a little strong...want is more apt. Wanting to change it up is healthy in my opinion and for me I'm doing that with crossfit.
I'll post some updates as I get back in shape and let folks know how it translates to my climbing. Don't worry, this won't become a crossfit blog - but I welcome any readers to send me what they've done in the past.