N.P. from the great state of Long Island asks if it’s okay to make multiple submissions when you are querying agents.
In a word: yes.
Do you have to tell the agents?
In a word: not really. Some writers will divulge that the project is with others. I see this as a courtesy, not a necessity.
What if two or more of the agents are interested? Happy days are here again. At that point you really must inform all of the agents that you have interest. This will accelerate the process, and if possible you should try to meet the interested parties in order to make an informed decision.
Don’t some agents require exclusivity? Sure.
Do I have to honor that? Sort of, but I wouldn’t wait for 4-8 weeks for someone to get back to me. Agents submit almost all of their projects to publishers on multiple submission for a reason. I think writers should enjoy the same benefits: it’s in the interest of time, and could potentially create a competitive situation.
How many agents should a writer go to at one time: I think the magic number is six. If everyone passes, it’s a useful pool from which to draw information. i.e. if you receive all form letters, go back to the drawing board. Close calls mean some tweaking is called for. Invitations to send the material, or see more material, this is a bullseye. Your query letter did the trick. Now, of course, the material has to hold up.
Did I leave anything out? Please ask or let me know where you stand with multiple submissions or your experience with them.
Betsy Lerner 
For some reason, my magic number was 10 (so original, I know). Within an hour of sending my query out via email, I had one agent request the proposal. As I was preparing to send it to her, I had another agent ask for the proposal, and he wanted a one week exclusive look. This was my first experience, and I was quite overwhelmed. In the end, I decided honesty was the best policy…I told him I’d be happy to send him the proposal but I had already promised to it another agent, as well. He was fine with it. By the way, neither ended up becoming my agent….it took another 10 queries and a couple of weeks before I landed the right agent for me.