Here are two of the best sites I've found about submission. In Writer Unboxed, Chuck Sambuchino lays out a submission plan that makes so much sense. Don't query 50 and risk the chance of having all of them turn you down. Test the waters with 6-8. Find out if your query is working. If it isn't, get help, then fix it, and then send out to another selected group of agents.
For some real nitty gritty Wowpaloozie stuff on all things Submissions take a look at Author!Author::Anne Mini's Blog. There's enough information about all things submission to give you the confidence to hit the query trail just right. Here's a small sample.
- EXCLUSIVES AND MULTIPLE SUBMISSION
- EXCLUSIVES TO AGENTS
- INDUSTRY ETIQUETTE, IS IT OKAY TO SUBMIT TO SEVERAL AGENTS AT ONCE?
- WHAT IF MORE THAN ONE AGENT ASKS TO SEE MY MANUSCRIPT? AND WHAT IF THE FIRST REQUEST IS FOR AN EXCLUSIVE? (Wowzer. Dilema, yes. But you can avoid this with some homework. See how.)