How to choose an immigration lawyer intelligently?

I have been trying to find a lawyer to do my NIW petition and I am a biomed PhD student.

For those who have passed NIW 140, would you help answer my questions below?
1. I am in Alabama. I heard my petition letter would go to Houston Processing Center. Does that mean I cannot choose an immigration lawyer in Maryland or California?
2. How to identify a lawyer is a real lawyer? I know I probably do not need to doubt a lawyer who has a website and phone number. But how do I know he is certified to practice law for my petition? Is it possible a lawyer passed California bar exam not qualified to file petition for me (I reside in Alabama and my petition packet would go to Houston to get processed).
3. Do you have positive or negative experience with the following lawyers:

Jerry Zhang http://www.hooyou.com.
Ken Liang http://www.kenzl.com/
Charles H. Kuck at Kuck Casablanca & Odom, Atlanta, GA
Miao Hai at www.jingchenglaw.com
Steve Qi www.sqilaw.com

Thank you very much! Hope to learn from you!