How should I prepare notes for my webcomic artist?

Some friends and I have been batting around the idea of making a webcomic, mainly for our own amusement. I’m doing most of the writing with input from friends, and I was going to try and outsource the artwork, either locally or to someone online if they have interest and a style that we both like. Before I start beating the bushes, however, I’d like to get a decent amount of material together that I can show prospective artists, to give them a good idea of what the project will look like and the kind of stuff we’re asking them to do.

I’m not really comfortable sharing details about the story or format, but when it comes to preparing some basic notes and outlines to show prospective artists, is there anything in particular I should do to to make their life easier? As it is, I was going to draw up a few sample panel layouts to show the kind of architecture we were looking for, pull together some on- and offline images to cite specific examples of the kind of look we want, and write a decent number of panels in screenplay format to give an indication of the comic’s tone, pacing, and the general feel of things.

So am I leaving anything out?