1. Read your teacher's work. (Analogy: would you let a carpenter whose work you've never seen remodel your kitchen?)
And if, having read your teacher's work you are unimpressed and/or turned off by it, do yourself and everyone else in the workshop a favor and do not sign up for the workshop. Please.

2. Ask him or her to autograph it. (An autographed first edition hardcover can be surprisingly valuable! And: flattery never hurts! Don't be shy about asking for an autograph; authors love this, they really do.)

3. Expect to learn. (Analogy: do carpenters learn their craft wholly on their own? Maybe what you'll learn is that this is a writing teacher to avoid. Certainly, this is much cheaper experience than having a bad carpenter mess with your kitchen.)

4. Realize that most people who come to a writing workshop have naive notions about the writing world (think money, celebrity, booze-crazed Bohemia), no clue from Adam how hard it is to write anything worth reading, how tough it is get published, and how consternating an experience it can be to be published (criminey, all these people taking your workshops who never even read your book!!). Realize, you are way ahead of the game by following steps 1-3, and that, therefore, though you might learn a lot about the craft, you do not need validation from this workshop, its leader and/or its participants, which is what you were secretly hoping for, no?

5. Expect to give thoughtful critiques to others who (though their manuscripts are surprisingly bad, not to mention boring and often tasteless), are, strangely, resistant and argumentative. Expect also to receive rude and deeply stupid comments on your manuscript and know that this, actually, is a good thing because learning to take criticism with open-minded equanimity is part of learning to be a well-published and productive writer— unless, that is, you want to be a writer who cringes at every review, every blog mention, every amazon.com shark attack out of Nowheresville, and is, therefore, both miserable and miserable to be around. (You can win the Nobel Prize and someone, somewhere, will say something unkind about your writing. So, Buck up.)

6. Despite all of the above, take very seriously your critiquing of other participants's manuscripts, for good karma and all that, but also because the fastest way to learn to recognize problems in your own manuscripts is by identifying the same in others's manuscripts. I think it was Ann Lamott who said (more or less), "we point, but do not cut, with the sword of truth." Read the pages carefully, and offer honest, thoughtful, and detailed critiques in a spirit of kindness. (Wouldn't you want the same?)

7. Remember the bicycle analogy. Like riding a bicycle, to take criticism productively, a writer needs to be able to balance between meekness (listening to everyone) and arrogance (listening to no one). Too much of either, your writing falls flat. (Too much of either and your whole life falls flat, now that I think about it.)

8. Do the assigned reading. To learn the craft, workshops are not enough (see again Tip #4). If you do the assigned reading while in a workshop, rather than later (or never) you have the inestimable advantage of being able to ask questions and discuss it with the workshop leader and other participants.
If, half way through the workshop, you decide that the assigned reading and/or discussion are bunk, oh well! Sunk costs are sunk! Surely you have better things to do and places to be.

9. Remember, what goes around comes around. If you come to the workshop with an attitude of respect and goodwill, you will attract the same. (Any exceptions you will, one day, consider hilarious. You can also put them in your novel, ha ha.)
That said, some people do not deserve respect or good will. If there are too many of them in a workshop, and/ or if the workshop leader is a disempowering nincompoop, I say, vamoose! As if the building is on fire!

10. Before, during, and after the workshop, keep writing. In other words, don't let the workshop deadlines become a crutch. Don't give your power as an artist to anyone else; find your own motivation, develop your own habits. Play God. God riding a bicycle.
Assuming that's what you want to explore in this life.