Seeing as I am actively querying, I thought I'd share something about my process.
The tool I use is nothing exciting. It's just a spreadsheet containing what I consider to be relevant details of each agency.
Probably too small to make out details here, so I'll zoom in a bit on each section...
One thing that throws up a red flag in this technological age, is an agency without a web presence. If I can't find a web site, and most especially if the site is unused or invalid, then I won't bother any further.
Sci-fi: This is a crucial question for me, and is trickier than it looks. Some agents are very explicit in ruling out sci-fi. Of all the genres agents might explicitly list as something they don't represent, sci-fi/fantasy seems top of the heap. It makes me feel very unwanted as a writer. A few (a very small few) explicitly say they do. This leaves a large grey and ambiguous territory in the middle.
There's also a lot of conflicting information out there. Searches for sci-fi on sites like Publishers Marketplace can yield apparent hits that are contradicted on agency websites. I usually look for several pieces of consistent information before labeling a definite "Yes".
That still leaves the many agents who accept "genre fiction" or "commercial fiction" with little additional information. Nobody seems all that clear on what that means. Sometimes all you can do is query and hope.
Source: When I started building my agent list, I felt it important to keep a note of where I first saw the name. It was a strange and confusing world, and I worried that I might not be able to trace back to the source of information. Now the names are like old friends, I don't pay much attention to this column.
Alerts/track record: Important information, especially alerts. I am careful to check sites like P&E and Writers Beware.
Contact: Most agencies have several agents, each with their own specialties. Before I query, I need to identify which (maybe several) individuals are candidates to contact. Of course, I will only query one agent at a given agency at any one time.
Submissions: A very important piece of information before going further. I use a cryptic code to list submission requirements, but it is fairly self explanatory. Do they want a query - not as dumb a question as it sounds, some agencies require you to submit via their web site! Do they want a synopsis or not? A bio? Do they want pages included (5 pages, 1st chapter, 50 pages) - the requirements differ. Any additional constraints, such as a short synopsis, or query word count limit.
Most importantly - do they accept email? I have sent some queries snail mail, but it is such an onerous process in comparison, that not accepting email submissions is a significant handicap in my opinion.
Of course, all these details are important to re-check immediately before querying. Agents move around. Is the contact I made a note of still at that agency? Submission requirements change. Alerts change over time too.
So, I'm curious. For those of you who are currently querying, or have done so in the past, does any of this sound familiar? Any other tips you'd like to share?