Let us suppose that you are a well meaning driver who wants to help out bicyclists, but you don't bicycle yourself (or at least not anywhere where you're sharing the road with cars) so you don't have direct experience to draw on. So, what can you do to help?

Paradoxically, one of the best things that you can do to help is to not do us bicyclists any special favours; to treat bicyclists just as you would any other vehicle (which is what they legally are, at least here in Ontario).

The problem with doing bicyclists special favours is that it makes you unpredictable, and bicyclists really want cars to be predictable. When a car deviates from what we expect and what it should do, we have no idea what it's going to do next; we have to slow down and assume the worst, not because we think you're malicious but because we just don't know what's going on.

The corollary to this is that if you do want to do a bicyclist a favour, such as letting them turn left in front of you, it will help a lot if you do something obvious to signal that you're doing it deliberately. This converts your unpredictable behavior (inexplicably slowing down, for example) into predictable behavior; ah, you're generously letting them turn.

(PS: please don't be offended if the bicyclist doesn't give you much acknowledgement of such things. Generally the best I can do is to give you a brief thumbs up in thanks, because I am otherwise too busy with the mechanics of signaling, turning, and so on.)