Focus on your strengths--so if your strength is more linework and their's is more coloring, you separate so one does linework and the other does coloring--helps keep it consistent. If you want to share jobs, just make sure there's a character bible with the proportions and character designs you can both reference, to make sure you keep it looking as close to the same looks as possible across the same comic. It does take some practice to though, to get used to blending your styles and learning what is easier to blend from other things. Luckily comics use so much that is more graphic design heavy than illustration--like laying out bubbles, panels, and compositions, that you will have plenty of work that isn't really reliant on character design at all.
