Find all the acting teachers in your area. Do a little sluething on your own, and try and get online feedback about them. Once you've got a handful of 'potentials', set up an 'audit' for the class. Every acting class will allow you to sit in for free on one session...do this until you find a teacher that meshes well with you.
Also ask around...other actors may know. You can also try www.backstage.com
and post on the forums there, or search for 'acting teacher' strings that talk about specific teachers.
It's important you mesh well with your teacher...and make sure you stay away from teachers that don't want you to talk about the class with anyone else...that's a red flag. Some teachers run more of a cult than an acting class...so don't fall prey to those people.