People usually have informal information networks, where information is passed through social circles, work places, or academic environments. Tap into these, sometimes they can get the word out faster than other techniques. Make sure you have a big sign, banner, or poster, that clearly states the name of your group or your purpose for being there. This is an ideal opportunity to distribute written material so make sure you have lots of copies on hand. Draw up a staffing schedule for members of your group so that everybody takes a turn.
Tables are also ideal for having petitions or selling fundraising items.
Canvassing - This means going out and approaching people to give them information. Make sure you have written information to pass out. This also holds true if you are canvassing people's homes. Always introduce yourself and explain to them why you have approached them. In the case of homes, canvassing would work well for an issue that is directly situated in that community.