1) Know the local laws. We didn't know we couldn't just set up shop in the Mall like that. We thought it would be okay as we had seen buskers there and also we weren't selling, but it turned out that we still needed a license. Thankfully, we got 3 1/2 days in before we got sprung.
2) If you're asked to move on, it's best to do so and don't try and argue it out with them. Don't make enemies of the locals and the ranger. Don't forget, there are many, many eyes watching how you react, and will form an opinion of you there and then.
3) Take time to make your display informative, interesting, and keep it tidy. We started off with a small display that was not so informative and wasn't that neat looking in 2007, but improved on it in 2008 and found people were far more attracted to something that was well put together and easy to read.
4) Wherever you set up, make sure you are not encroaching on someone else's space, are not blocking walkways, shop ways etc and that you have room for people to stop and look at your display without stopping the flow of traffic wanting to pass by.
5) Dress in clean clothes and look tidy. You're trying to reach everybody, not just one type of person. We found long hair didn't put anyone off, as David wore his hair tied back and wore a smile (usually a winner right there). Be careful of any slogans on your chosen t-shirt - some things offend certain people and might also draw attention away from your subject and what you have to say.
6) Don't waste time on people who only want to argue. There are plenty of people who really do want to know, but it can be off putting if they see you and someone else having a heated argument. If you have a few people (or even two), take the person who you want to get away from the display off somewhere else
7) Make sure you've either got a packed lunch or can go somewhere close to eat as you want to spend as much time talking to people as you can. We found that plenty of water was a must too.....talking makes you very thirsty.