The following are suggested ways people can work to help combat street harassment at an individual and grassroots level:

Individual Level:

In the Moment:

1. If you feel safe enough to do so, confront the harassers calmly, firmly, and without insults or personal attacks, to let them know that their actions are unwelcome, unacceptable, and wrong and why. Use tactics suggested by Martha Langelan and the UK Anti-Street Harassment website. Here is advice from Martha Langelan on dealing with drive-by harassers.
   
   
2. Hand the harassers a business card telling them not to harass women. Here are three you can download and print (print on plain paper and cut or use Avery 8373 business card paper):
   
   "Advice for picking up women" front ~ back                               *
   "Show respect: Do not harass women!" front ~ back                **
   "Wait a minute! What did you just say?" front ~ back               ***
   
   
3. If the harassers work for an identifiable company, call or write the company to let them know that their employees are harassing women and why that is unacceptable.
   
   
4. Intervene when someone else is being harassed to help her out of the situation and let the harasser know that his actions are not condoned by others. Men engaging in this tactic can be particularly powerful since men look to other men for approval.
   
   
5. Take actions that will create real consequences for the harasser, such as reporting the person to a police officer or other person of authority, like a bus driver or subway employee. [NOTE: Here is a statute in New York against serial ats of public lewdness]

Before or after being harassed

1. Talk about your street harassment experiences with family, friends, coworkers, and acquaintances. A lot of people don't realize how often it happens and how upsetting it is. Maybe if more people knew, it would happen less.
   
   
2. Put up anti-street harassment fliers, posters or signs (click on link for street signs) or hand out anti-street harassment fliers. Here's another example of a street harassment poster.
   
   
3. Write and submit an article about street harassment to a magazine or newspaper.
   
   
4. If you are in a position of mentoring (as a family member, teacher, or friend) educate boys not to speak with disrespect to women and teach girls how to stand up for themselves and challenge disrespectful behavior.
   
   
5. Volunteer time or donate money to fund anti-street harassment organizations, workshops, or community projects.
   
   
6. Take and/or encourage others to take self defense classes so they feel more empowered to safely confront their harasser(s).
   
   
7. Post your street harassment story or tactic suggestions on a website or blog.

Grassroots Level:

1. Join or start an activist organizations such as the Street Harassment Project, Rogers Park Young Women’s Action Team, RightRides, or NYC SafeStreets to work to end street harassment in your area.  It not only raises awareness of the problem but concretely aids women dealing with street harassment and works on preventative measures so women are not harassed in the future. 
   
   
2. Create a lobbying group or petition for anti-street harassment ordinances in your city or state so that people who have had serious incidents of street harassment and want to seek legal recourse can have a way to do so. 
   
   
3. Organize or participate in a lobbying group or petition for inclusion of school programs that teach respect for one’s peers at every grade level.

While ultimately street harassment, rape, and domestic violence are unlikely to end until there is a cultural respect for women and an end to the idea that women’s primary identity is as a sex object, the above are suggested ways that people can take to try to help that cultural shift occur and help stop street harassment.  In doing so, I do not want to ignore the fact that men must be educated to stop harassing women and that it's not a woman's responsibility to stop harassment, but rather my suggestions are for those who would rather take the matter into their own hands and act instead of waiting for men to figure out that it's wrong to harass women and that they should stop.

NOTE: I am not professionally qualified to offer advice on street harassment. My suggestions are based on the research I conducted for my master's thesis on street harassment. The suggesitons must be practiced at your own risk. There is no one way to address every instance of street harassment and it is up to you to decide what will be the best way for you to act to maintain your safety and dignity.

* Thanks Michelle for this idea
** Thanks mom & Mary for your suggestions
*** Thanks dad for this idea