New graphic novelist

Well first you need a concept, and it needs to be a concept of the right length (160-220 drawn pages). Making an outline helps you make sure your plot isn't missing any pieces and adds up to the correct length. Might want to run that past some people for feedback. Then visual designs for the characters, because if you don't have their look nailed down you will end up needing to redraw the first scene to make it consistent with the rest. Some people write an all-word script first, others do thumbnails. Then finally the actual drawing, one page at a time.

I would start with a short story. Maybe it could be the prologue to your novel, or something related to one of the characters. Six pages should be enough. It's good to play around in a sandbox first. That way you can try out character designs without getting wedded to them, experiment with size, materials, etc. When you start your book, don't worry too much about getting the first scene just right. You probably will end up redrawing it later on, actually, you should count on it.

A sandbox is a metaphorical place to play around and explore techniques and your medium.

Don's advice is excellent.

Look at the sticky thread here about writing a comic. There are books you can buy if that's your preference.

However, being good at drawing is a WORLD away from sequential art. There are lots of stunning artist who simply can't do the page after page after page containing panel after panel of consistently awesome artwork.

If you CAN, more power to you. This is just an observation I make and not intended to put you off, rather to forewarn you so you don't get discouraged if this is you. You can always find an artist later if need be.

I'm a big fan of the outline. Where does the story begin and where does it end, and what's got to happen to get from the beginning to the end. I lay it out in chronological order so I know the sequence. I don't necessarily write in chronological order but I find it helps me if I know my story before I get down to the actual writing. Anyway, as I work on this outline I also make note of any visuals I want to include. I don't draw but I'll want to be able to communicate what I "see" to the artist.