As a fellow commuting cyclist, I find that the most effective "tool", by far, is constant awareness, and a significantly reduced faith in humanity.

I assume that everyone is distracted and not paying attention to what they're doing, and that informs my "riding rules": Try to make eye contact, don't assume you've been seen. Never be in the blind spot. Never pass on the right. Cross on a red light to get ahead of the pack of cars.