After I've written a story, but before drawing it, I make rough pencil versions with lettering of every page. They're called layouts because it's a chance to figure out the size of each panel, how many speech balloons there are and where they're placed on the page.
If things aren't working out then I try another layout to solve any problems. It's quicker to re-work a pencil sketch than a finished page.
As a comparison between the layouts and the end product, you can see the coloured page below.