Table when you have something for people to do, and not just for the sake of tabling. Try to table where there will be a large concentration of people. Dining halls near meal time, Student Unions or Centers, and films and events attract a lot of people in a short time. Its best to have two or more people tabling together, preferably pairing less experienced people with veteran activists. Have one of them work the flow of people and draw people to other activists sitting at the table.
Training is invaluable.
Write and distribute sample raps and practice with role plays. This gives people confidence and prepares them to deal with tough situations. Display a banner with your organization's name to develop recognition, a sign and flyers advertising your next meeting and upcoming events. If you are collecting letters, be prepared with paper, pens, envelopes, a box for donations to help with mailing costs. Collect letters there to ensure that they get written and sent.