This blogpost is for anyone who does public activism, but since this is an animal rights blog, I will talk specifically about animal activists.
When being an activist in public, especially while out on the streets, it's important to have a certain look. Having knowledge about the cause is great of course, but your public activism may fail if you lack the proper appearance.
For example, which group do you think people in general will be more drawn to, will stop on the sidewalk and pay more attention to what they're saying?:
The people in T-shirt and old jeans.
The people (if female) in a casual but nice looking dress and (if male) in a nice shirt and wearing casual pants but not jeans.
How one dresses is important because it makes what you're talking about look more important and you are more likely to be less intimidated if you dress nicer. Also, regardless of whether it's cool or not, having multiple piercings and tattoos on your body is very intimidating to some people--especially older people. As animal activists, want to come across as being extremely approachable, so you need to look as less threatening as possible. It would be best to take out the multiple piercings and hide the tattoos with your clothing. Appear as if you were going on a job interview because, afterall, animal activism IS work.
Activists don't have to wear a suit and tie or wear stunning evening dresses--dressing causally nice is best--but if you were to dress like that and compete for people's attention on the street, you would probably get more people coming toward you than activists wearing T-shirts and faded old blue jeans, even though both groups are speaking on the same cause in the same way.
The exception would be if your group needs to wear costumes and do theatrical scenes to make a point.
Also, to attract more people and to be taken more seriously, try to find older people, like over 30, to participate in your street activism. People in general tend to pooh-pooh groups that are made up of teens-20s as stereotypically just a bunch of "rebellious kids" to ignore. With a healthy mixture of ages, people will more likely stop and pay attention if some of the activists are in their 40-50s or older.
So, next time your group goes out on the street to speak out for the animals, make sure you not only have the knowledge to speak on the cause but the appearance as well to make people stop and listen to what you have to say.