Refuse to do anything that might be seen as physical violence at Trump events; loudly proclaim a commitment to strict non-violence; learn and practice tactics of non-violent protest.
Why is this important?
Corporate mass media will focus on even the slightest evidence of violence from anti-Trump protesters, to make it look like protesters are inciting violence. Many voters will be swayed to be more sympathetic to Trump. So even the slightest hint of violence from protesters will end up helping Trump, perhaps enough to get him elected. That's why Trump wants to incite violence against his supporters. The message of non-violence has to be amplified, loud and clear, by all anti-Trump protesters, so there can be no valid claim that protesters are responsible for violence. Non-violence can be very difficult. It has to be learned and practiced. That's the best way to stop Trump.