Make sure you are familiar with all the types of information you should be collecting. Practice with your partner so that you become comfortable with logging the video or photographic data onto the Legal Observer Notes form. In addition, review the appendix on typical charges and defenses, so that you know what will help prove that people have been unlawfully arrested. Figure out the standard width of the streets and the sidewalks in the vicinity in which you'll be observing. The other member of your pair will need a camera, still or video.
Disposable cameras are fine, too.
Get far more film or tape than you think you'll need. You should have a cellular phone, radio or pager with you. Otherwise, it will be impossible for the Legal Observer Coordinator to direct you to the places where you're most needed. If you don't own a cell phone or radio, borrow one. Binoculars or a small telescope may be helpful, as well.