seconding the link to the nitty gritty tips thread, those threads are really great.
also, you may have noticed vertical format comics are very popular on tapas; where you have one panel for the width of the page, and then you scroll for the next one. theres lots of pros to this, its easier to control the pacing and easier to keep things clear, and people certainly wont complain. however, traditional page formatting (rows of panels like you see in most comics) might leave more space for fun, and have more references out there on how to do interesting and effective things.