Normally I start sketching process with some random letters, numbers, words, - just to get the feeling of the future font. Sometimes (50 pages later) I find something that catches my eye and that just feels right. And I start to add more stuff like that.
I've been planning to take some photos of an actual process for a while, but usually I get caught in the process so much that I don't think about a camera. When I'm done, I have about 20 pages that look like the one below.
Sometimes I already know how I'm gonna call new font - then I write the name somewhere in the corner (you can also check out how my actual writing looks like - yep, I also don't understand it most of the time).
If I don't - I just call it "Font128" or something and figure out a name later. By the way - naming fonts for some reason is one of the most exhausting parts of a font making process for me.
After I think I have all characters, numbers, symbols, etc I trace images into Illustrator and pick the best glyphs in my opinion for the future font. Usually to do so I'm creating some short stupid phrases - just to make process more fun. Some dozens of hours later font is converted into hand drawn letters into a real thing and I play with presentation.
For this particular one I used handmade textures (had TONS of fun creating them, then spend 2 hours cleaning the floor from an ink - that part wasn't as fun :).