I recently responded to an author's questions about making an agent change. I thought perhaps there are others looking for this kind of info and thus, I'm posting the bits below on my blog for general consumption.
Please, remember, I offer this advice without any knowledge of the details of any one person's situation. If you have doubts/questions regarding your specific situation, you may want to contact an attorney. I did. And it was a good thing. At times where emotions are running high, having someone who is level-headed and looking at the situation from a more objective point of view can be a HUGE help.
Anywho, following are a few general suggestions regarding changing agents:
1. First things first. You MUST take a look at the contract you signed with your agent (assuming you had something in writing--not all agents require a written contract). The contract should have a separation clause detailing exactly what steps must be taken to cut ties. Usually it takes the form of a letter. Also, check and see if there's a specific timeframe for contracts on submissions. I think 60 days is common. This means if a contract is not offered within 60 days from the date on your separation letter (or whatever timeframe in your contract), then your agent loses claim/interest in the deal and it's open territory for a new agent.
2. Take a look at your current inventory. Do you have another book/proposal to submit to a new agent? If not, you might want to wait until you do.
3. Once you have something to shop around, go ahead and write the letter to your current agent. It's pretty much a given that agents will NOT look at you (at least not seriously) until you've taken this step. I know it's scary because you're giving up a sure thing (even if it wasn't working for you) for an unknown. What if you don't get a new agent? But it's a necessary step if you want to move on. BTW--Mail your letter registered mail.
4. Make a list of agents, ranking them based upon your level of interest. Do your homework ahead of time--talk to authors the agents currently represent. Talk to past clients if you can find them. Ask what made them move on. Then submit, submit, submit--starting at the top of your list and working down. Queries should go out in batches of 5-10. Get a few rejections? Send out another batch.
Finally, I've found it's helpful to mention you were represented by an agent but are making a change.
Go Ahead, Share Your Thoughts! .