Regarding thumbnailing/story boarding, I can't recommend it enough
it makes the process of actually putting pencil (or tablet pen) to paper/tablet so much easier since you know the rough emotions each character has, their pose, and most importantly that the text will fit well. I'm currently working on my first project which is a "short" one-shot, so I decided to rough out the whole thing before I started. Here's an example of one of my spreads:
Like roughing out a page at this level of quality doesn't take too long, and if you add the text at this stage, you can easily see if it'll actually fit or not. If the text does fit, awesome! That panel is good to go. If it doesn't, you should erase and redraw (or use the marquee tool or equivalent in whatever program you use, if digital) the stick figures around until the text and pictures can live together in harmony xD Then after that's worked out, you can move on to the much nicer actual page/panels. And like even as you're doing the real page, you can still nudge things around depending on how the actual art looks and stuff, but by doing this kind of prep work up front you can feel fairly confident it'll jive. That page on the right in my example is by far the wordiest page in the whole comic, but I managed to fit everything in the final version I finished last week :]