I have a number of questions for you to consider asking agents, or go to their websites and look for those answers.
• Are you a member of the Association of Authors' Representatives?
• How long have you been in business as an agent?
• If I want to contact you, how do you prefer I do that?
• If I make contact in your preferred method, how long should I expect to wait until I hear from you? (If I don't hear within that period, what should I do?)
• How do you keep your clients informed of your activities on their behalf? Will you inform me of all responses to my work? Do you do that as they come in or send me a list?
• Do you have specialists at your agency who handle movie and television rights? Foreign rights? Or are you proficient in those areas?
• Do you have subagents or corresponding agents in Hollywood and overseas?
Even though those are good questions, agents may not respond to them. You also risk the possibility that the agent may label you as HMA (High Maintenance Author) and choose not to represent you.
Before you sign with an agent, learn about the agent.
This will be a long-term relationship, so be careful.