Search the Internet for a list of public relations firms that deal in entertainment. Entertainment directories such as LA411.com and NY411.com are good places to start.
Create an information document about yourself, known in the public relations field as a backgrounder. This includes information about you, your needs, objectives and desired outcome.
Send your backgrounder by email to the contact at the PR firms you have selected. You will get a response from that contact indicating whether it is interested in working with you. If you like the responses, ask it to send you a capabilities package. This will include information about the firm, its expertise and personnel that would be dealing with you directly.
Meet with the publicist from the firm you have selected. There are no obligations in this meeting as it is simply to see if you and the publicist are a good fit.