I found the booklet Engaging Bystanders (pdf) by Joan Tabachnick and it is a must read for those who want to enable people to act productively in rape prevention before sexual violence has been completed.
This engagement of bystanders is far more than changing actions in situations where violence is in progress. Although emergency intervention on the part of bystanders is important if that's all bystanders do to prevent rape they aren't doing enough to change the rate of violence since most sexual assaults are committed when no bystanders can see to intervene.
The larger goal is to engage all non-violent people on a society-wide scale. This is what is needed to create a safer environment where sexual violence is always actively deterred. At the foundation of this bystander effort needs to be the absolute rejection of viewing any victim as the root cause of that person's rape.
Right now the mixed messages from respectful people about when rape is acceptable or when rape isn't "real" rape or when rapists aren't responsible for their actions helps potential rapists to minimize the harm they are doing and helps them to put the all the responsibility for stopping them onto the other person.
Those who say that little girls in sexy clothes cause men to want to rape little girls give child rapists a scapegoat for their decision to commit child rape.
The truth is that it is the thinking of child rapists which causes those rapists to rape little girls in sexy clothes just as it is the thinking of child rapists which causes rapists to rape little boys. This is true for all demographics of rape victims. The cause of all those rapes is the thinking and decisions of the rapist.
The thinking of bystanders can echo sweetly in the minds of rapists or it can sour the thinking of rapists. Bystanders often hold a mix of attitudes so they support rapist's thinking only in certain scenarios. Changing our own thinking so we absolutely reject all rationalizations for rape is within our power even if it can be difficult because of how pervasive victim blaming is in our society.
If all bystanders sour the thinking of rapists there will be fewer rapists and those who remain will have a tougher time fooling juries that "it was consensual."