The best way to start is usually with an introduction.
The worst way to start a blog would probably be by telling you to go and look at another, far more interesting blog.
So here is Heath Lowrance's excellent introduction to the history of noir/hardboiled fiction. It is currently influencing my reading list as I try to catch up on some of those old American pulp writers who have passed me by thus far. As well as being author of The Bastard Hand (New Pulp Press), Heath writes the always interesting Psycho-noir blog. Check him out.