Paying for Classes.

You should ALWAYS, and I mean ALWAYS be excercising your skills by getting as much stage time that you can.
There are FREE opportunities to do improv, and there are PAID opportunities to do improv.
As far as improv classes are concerned, most of the times the old addage that "you get what you pay for" seems to be true. Although I currently am pursuing a free opportunity as well as a paid one. In taking a FREE class you give up certain things that you dont have to give up with a paid class. For instance, in a free class I will have to be subjected to some pretty stanky level performers, and possibly some stanky level intstuctors. I dont have the right to say, " I dont like this or I dont like that...why is this person in the class etc." Its FREE!
If the instructor wants to lecture 90 percent of the class time and only allow you onstage for ten percent....its FREE.
On the opposite end, there are classes/schools that are WAAAAAY over priced!
In theory, I beleive that you should have to pay something. Even a low-budget "token" payment. You will value something more if you are paying for it, even if it is three dollars a class.
you will show up on time and regularly to make sure you get your money's worth (pre-paid).
You will respect your teacher/instructor more.
On the other hand, you could easily be suckered into paying way too much for a class that you could get the same value at one third the price. Easily.
That decision must be yours to make. What are you paying for, and what is it worth to you?
Are you paying for the right to put a prestigeous name on your acting resume?
Are you paying for the opportunity to someday be advanced into a widely respected improv troupe?
Are you paying for time with a "name" instructor who has a legendary reputation in Improv?
Well, maybe all these thing are worth it to you then, to spend the overpriced tuition.
If you just want to learn the craft and be surrounded by people who are very talented and inspiring, and "name-recognition" is not important to you....then I would suggest something IN-BETWEEN the free classes and the over-priced classes.

You want to be surrounded by people who are slightly above your level, so that you can be brought up to their level. However rewarding it may feel like...you dont want to be the "star" of your class, or the most talented or skilled.
You shouldnt be with a class that is way above your level either. This might damage your ego to the point that you think you are worthless or un-talented.
Find a challenging class taught by a capable instructor that is affordable.
And by affordable.....in 2009 prices, I would say anywhere between 60-200 dollars a month.
(once a week classes at two hours).

If you can combine, like I do....going to a paid class and a free class...better for you still.
Consider Community Colleges, Recreation Centers, Meetup Groups etc. as low budget or even free options.

When deciding to bust out the wallet and pay for that high priced class...do your research. How respected are they? Where is the instructor from? What is their curriculum like? Who are their graduates? How many students per class? How much stage time can you anticipate? What are the requirements for going up to the next level or making it to the mainstage performing group?
What are their payment plans and cancellation fees? Can you "Audit" a class or instructor to see if you like it before paying?
Check the internet...better business beauro....craigslist etc.
Word of mouth is probably the best and easiest if you have a lot of friends in the business or are pursuing the business. What do they think? What has their experiences been?

Good luck.