When an agent calls you on the phone, it doesn’t mean that they will already accept you as a client. It only means that they are inviting you for an interview and then see where things go from there.
The questions they will ask are similar to what a recruiter will ask you when you are applying for a job and when you reply, elaborate on it as thought you are telling a story. That way, they will know that you are very articulate and they can already think of ways of how to sell you to casting directors and producers whenever there is am upcoming movie or a new television show that is about to come out.
It wouldn’t hurt to also act in front of the agent a part you performed in the past so they can also get an idea of what is range.
If the agent likes you and wants to take you in, ask yourself if you feel the same way about the agent. Should the feelings be mutual then you have already found someone that can look out for your acting career. If you are not happy, don’t be afraid to decline their offer and look for someone else.
One thing you should remember when looking for a talent agent is that you are not required to give them any show money before they decide to represent you. If you are not happy with how your acting career is going, talk to them about what changes need to be made because your acting career is on the line here which may not mean anything to them if they represent other actors.