I spent a couple days working intensely on this mermaid illustration. I'm trying to slowly add more to my childrens' publishing portfolio.
I started out with a few sketches and chose a composition I like. I'll probably tackle one or more of the sketches in the near future to sort of build a story around these characters.
Usually I work really roughly in my sketches. If I feel I need to sort of develop the characters or elements more, I'll do a more detailed drawing (or series of drawings if need be).
Since I'm really comfortable working in Illustrator, I usually don't need much more than a very rough sketch. I prefer to scan in my sketches, as opposed to taking a picture with my phone. I dunno, I can never seem to get the lighting or angle just right to avoid distortion or an ugly shadow.
I'll start outlining shapes in Illustrator. Normally I have an idea in my head when it comes to colors and if I want elements to have some kind of textured edge. I have a set of art brushes that I have on hand that I enjoy using to add more character and a hand drawn look to the illustration.
If you are unaware of how drawing in Illustrator works, each element (both lines and shapes) are all separate and can continue to be edited and tweaked. I usually organize things on different layers and group objects to make working and moving things around more easily. The only texture I add in Illustrator comes from my hand drawn brushes.
Finally I add a lot more details and textures in Photoshop. I prefer this way because it's easier to manipulate objects and I can hand draw (using great brushes) textures. I also add gradients with noise and watercolor textures. Photoshop does a better job with adjusting the brightness, saturation, lighting etc that I can't really control as well in Illustrator.
Here are links to some of the tools I used: