Instead of rioting and causing property destruction that is rarely interpreted properly, here's a thought.
Position yourself between the police and the peaceful protesters. Act as a barrier between the police and those who want to have their peaceful say so they may actually do so. Link arms, sit down, but do not antagonize. Perhaps use that time to engage the officers in dialoge but don't be an ass about it.
Force the police to strike the first blow. For this to work it must be clear that they acted first, unprovoked and our response is measured. The key is to not antagonize. Allow them to increase the tension and and respond in kind. Tactics will be met with equal tactics.
Love will be met with love. Fists will be met with fists. Tasers and tear gas will be met with equivalent tactics. But that is not that goal. The goal is to protect the peaceful protesters from the repressive forces that would shut us all up permanatly.
(The whole efficacy of marching is up for debate in my mind but that's another post.)