Create a demo of music to be sent out. The demo should be on a CD and highlight a handful of your best songs. Three to five songs is enough. The CD label should have contact information on it, such as your name, telephone number, website and email address.
Create a second CD. This CD will not have music on it, but it will have other sorts of DJ-related info. A picture is good practice to include, as well as any press coverage that has been achieved. A list of clubs played at can be good to include if the clubs are larger or have a good reputation. Photographs should be professionally taken.
Label each CD clearly. Put them in two separate cases, and mail them to labels or radio stations. Be sure to include anything else that may be valuable to the viewer(s), and be sure to address the package to the proper person(s).