Read Effective Cycling. Maybe your library has it or can get it. There's a whole book full of techniques. One of the most counterintuitive bit of knowledge is that in the daytime, being rear ended by a car is about the least likely thing to happen, yet it's what inexperienced cyclists fear the most. So when it's not safe for a car to pass you in the lane you're in, don't let him. Move left to occupy the whole lane, to prevent him. Then move over when it's safe.