In everything that you do in your writing career, be as thorough as possible. For your own sake. If an agent represents your genre, and you think they might be a good fit for you, good! It means you've done your research. At least, if you come to that conclusion it SHOULD be the result of research. If not, go do research. Do it now!
But let's say that agent accepts your work and offers you representation. Do you say, "Yes, absolutely, without question!"?
No. Do some more research. Are they making an industry-standard offer? If they require a higher or lower percentage of all sales, ask them why. Read your contract. Are YOU the client, or is your IP the client? If they leave the agency, do you go with them or get sent over to another agent?
More than that, can you WORK together? Based on interactions that far, do they seem like the type of person you'd be willing to work with for the next 20 or 30 years?
Don't just agree to a business partnership because they asked. Make sure the opportunity is the RIGHT one. Be careful, though, because saying no just because they're not your "dream agent" could cost you a great working relationship. At the end of the day, if you don't see yourself working with that agent long-term, try not to waste their time by making them jump through hoops just to have you tell them "no thanks."
It goes back to my first point: be thorough in your research.