While there's nothing better than some good instruction, I'd like to add a cautionary note - be certain that your instructor is compatible with what you want to and how you turn (unless you're starting out!).
As an example, while I really like Stewart Batty, he insists on sharpening techniques that don't work well with my preferences. He's very entertaining and has great knowledge, but like many name turners, he wants you do do things his way only. There are others who will insist on you using tools with only the profile they espouse (Ellsworth is one), some that insist you use certain techniques and not others (waste blocks, jam chucks, etc., etc.).
I'm certain a good part of this has to do with an instructor having some control over the variables in the 'classroom', but since there are many, many different ways to accomplish the same thing in turning, make certain you have some level of agreement before committing lots of money.