Go to the clubs or venues where the band wants to be booked. Even if the booking agent is not available, make an effort to meet people anyway. Many times it is possible to meet someone who has a connection with a different venue. Getting in touch with people in the band's music scene is paramount.
Carry business cards that contain the band's name, logo, website and contact information at all times. Keeping them in a small metal case will ensure that they stay crisp and fresh for important contacts.
Create an electronic press kit for the band. It should include footage of the band performing, concise biographical segments on each band member, contact information and anything that sets the group apart. If the band has played any major festivals, toured with more recognizable bands, has a large fan base or endorsements, the press kit should mention it.
Send the band's electronic press kit to connections that may lead to a gig. However, do not blindly email people and hope for the best. Stick to people you've made a personal contact with. If the interaction went well, the chances of scoring a gig are higher.
Follow up with every person you contact. It is very easy for a busy club owner to look at a press kit, love it, but then get sidetracked with something else.