Your booking agent is the person who makes the arrangements for your show, gets all the contracts signed, and makes sure you have what you need in order to put on your show, for example, proper lighting. The booking agent gets a portion of the proceeds from your show, called a commission, usually 10 to 20% of your gross earnings. In return, you and your band promise you will show up at the promised time to perform. You will most likely need to sign the contract yourself, since you are the one promising to show up, but sometimes you can give your booking agent the authority to sign the contract for you. If you have a manager, he or she would most likely be the one to sign the contract.

Artists who are more established in their careers may ask that their booking agent clear all bookings with them or with their manager. Artists who are not quite as established may allow their booking agent to sign for all performance contracts on their behalf.
 
Caution must be exercised when looking for a booking agent. The booking agent can make you as a performer or can break you. This is a business agreement and must be approached as such. In other words, the booking agent is not necessarily your friend, even if they are extremely nice to you. They are in the business to make money, just like you are.

The best way to secure a booking agent is to put together a really good press kit and send your press kit to several different booking agents. You may want to invite the booking agent to come see you at one of your performances. 

Take care to sign with the booking agent you know you really want to have. Don't settle for anyone you perceive to be second best. It is far better to wait for the right opportunity than to sign with a booking agent you are unsure of. (See above where it says the booking agent can make you or break you.)

You want a booking agent who can book you into the venues you want to play. You want a booking agent who really believes in your product (your music). You may not want a booking agent who seems to value the venue itself more than the artist (you).