Aspiring writers are encouraged to query widely in order to increase the chances of finding representation. I agree but I also think we should query wisely.
Not all agents have the time or the inclination to maintain a blog but I love those who do. You receive valuable insight not just on which genres they represent but how they think and interact with clients. You have a better idea if they will mesh well with your ideas and career goals.
Research every agent that you decide to query. Websites and submission guidelines will often tell you if they are editorial agents or not, the particulars of what they are interested in, and who they currently represent. Ask yourself if it is important that they represent multiple genres or specialize in yours? Do you plan on staying with this genre or do you see yourself branching out in the future? If so, will this agent still be a fit for you? Do you need someone to give you that added help before submitting to publishers or is your ms ready to go? Be honest.
It may not be possible to know details about every agent that you query but make the effort to find out what you can. It is important to have a list of questions ready for when that offer comes but if you know who you are querying before the call, then you are already ahead of the game.