“How many clients has the company added in the past year?”
I would prefer trying to assess growth rates outside the interview. In many cases, you should be able to get an idea some other way. This question shows lack of initiative. And, in many cases, the interviewer may not even be permitted to answer it.
“What has the employee turnover rate been over the past 24 months?”
Too much focus on the negative. You don't like when they ask, "Why did you only stay with Company X for 3 months?" They'll feel the same way.
“What’s the company’s policy on work/life balance?”
You might as well say, "I intend to deliver 40 hours of my time for 40 hours of pay. If you need extra help, ask someone else. Big turnoff.
“What kind of tools are provided to help me do my job?”
Better: "What kinds of things do you need me to do to help the company achieve its goals.
“In the first 60 to 90 days, what’s my first priority?”
Actually, this is a great question. It can paint a good picture of your life and shows that you're ready to get to work.
“Are employees required to sign a non-compete contract?”
By asking this, you are identifying yourself as a problem. If someone asked me this question, the first thing I would think would be, "What is he up to and what is my risk?"
For technology companies, just assume that the answer to this question is "Yes" and sign it.
When interviewing someone else, I appreciate good questions. They show interest and possibility. But I get a bit concerned when too many questions are of the variety of "What's in it for me?"
I think it's always a better idea to present yourself with President Kennedy's attitude: "Ask not what the company can do for you, ask what you can do for the company." Find a way to present yourself that way while still learning everything you need to know.