Collaborating is something that has to be experienced to understand. When a writer can see his vision come to life, it feels unreal. Here is what you need:
You need to have several short stories already completed. If you don't have a small library of your own work than start writing. Try to have a variety of genres. You don't know what a potential artist might be interested in drawing.
Approach several artist. Many will likely not see your story the way you do. Maybe the artist would be good for a different story you have, or their style might be better suited for someone else.
Be careful before chosing an artist. Ask to see a sketchbook or a portfolio of their work. You want to know what you will be getting into. Make sure they are willing to ask questions along the way. This is not something one idly hands off and waits for the results. There will be many questions along the way. Hopefully you will be involved in the storyboarding process, or thumbnailing. This is where the artist makes rough illistrations of what the layout will look like. Let the artist take the lead here, they will likely know things about visual storytelling you have not considered. The point is, you want someone is going to be a partner in translating your work.
Once you have done this form of wholesale version of collaboration you may get to know the mindset of your artist or writer. After you do this, you are ready for a true collaborative storytelling process. One where the two individuals are able to shape the story as it is thumbnailed. Until you get this tightened connection of the minds, please stick with finished stories that you are willing to be flexible with.
Nothing is worse than an artist sitting in a holding pattern, not knowing what comes next. Take care of each other and let the awesomeness ensue!
Thanks for reading.