Create a proposal. Before you even start writing the actual book, you should know what you're writing about. Plus, contrary to what you might think, it's the proposal, not the book, that will land you an agent, and although you won't need it right away, if you're lucky, it won't be long before you do.
Research literary agents. If you think you don't need one, then think again. None of the major publishing houses accept unsolicited manuscripts. This means that, in order for your book to be published, you will need an agent.
Find at least 20 agents who represent authors similar to you. If you're writing a non-fiction piece, for example, you will want to find agents who specialize in non-fiction.
Write a query letter and submit it to the agents you selected. Be sure to include a self-addressed and stamped envelope so the agent can contact you if necessary. Wait for a response. Typically, if an agent is interested, he or she will contact you quickly -- usually by phone. If the agent isn't interested, then you'll most likely receive a letter instead.
Compare your options. If you're one of the lucky few who interests more than one agent, you will need to do your research. Find out what authors each agent represents, how many books he or she has sold and which publishing houses the agent typically works with.
Send your proposal to the agent you've selected. You should only send your proposal to one agent, so make sure you choose the right one. Wait to hear back from the agent. It usually will take an agent four to six weeks to review your proposal and get feedback from other agents.
Notify the agent that you will be submitting your proposal to other agents if you have not received a response within six weeks. When you inform your agent of this, you should give him or her at least one more week to respond. Submit your proposal to the next agent on your list. If you don't have another agent, then repeat the process and select 20 new agents. You may also want to consider restructuring your query letter at this point.
Sign the contract. If an agent accepts your proposal, then you're ready to start writing. Now all you have to do is make any requested changes to your proposal and wait for the agent to make a deal with the publishing house. Once that's done, the hard part is over and all you have to do is write the book or screenplay.