To produce effective change, you need to have concrete, actionable proposals that will receive support.
In a political system with first-past-the-post, single-constituency voting and an intelligent, informed, well-meaning and constructive electorate, that means you need to be passionate, you need to be articulate, you need to have the facts on your side, you need to be committed to your idelogical goals, and your idelogical goals need to be a little bit, but not too much, slightly off-center from whatever current policy is.