You've got your manuscript finished, beta-read, edited, and polished. You're confident it's ready to go. You want to try for traditional publication, so you know finding an agent is the next step. You've done some research, so you know you'll have to query to find the right agent. But that's not all you'll need. If you're getting ready to enter the query trenches, here's a checklist of things to do before you begin.
1) Prepare your list of agents. Make sure you do your research and develop a list of agents you'd want to work with if they decide they'd like to represent you. Check querytracker.com, Publisher's Marketplace, and of course, the agent/agency's own website for details. Double or triple-check each agent's submission guidelines to ensure you're sending exactly what they're asking for.
2) Write and polish your query letter. There are lots of resources out there for doing this, but you can't do better than reading every entry on queryshark.blogspot.com. When you've completed your query, give it to a couple of critique partners for input. Often, you'll be so close to your manuscript at this point that you won't be able to read your own query objectively.
3) Write and polish a synopsis. More and more agents are asking for these, and it makes sense to have one in your arsenal before you start querying. I suggest writing a long (5 page) and a short (2 page) synopsis so you can send whichever one is requested. Check out my posts here for plenty of tips on writing the synopsis, along with my 14 synopsis critiques!
4) Clean up your social media presence. Some agents will do their diligence on prospective clients before signing them, or even before requesting more pages. Make sure your Twitter, Facebook, and other social media accounts reflect what you want an agent to see in you.
5) Create a submission tracking system. querytracker.com is great for this, or you can create a chart or spreadsheet to keep track of who you've submitted to, when, and what the result was. You don't want to accidentally double-submit to someone, and being diligent about tracking is the best way to avoid this.
Best of luck to all of you, and QUERY ON!!!