This is the first step for any project or site I've built.
Taking either a wishlist of features, or a design requirements document, I start out with simple pencil and paper to get down quickly a rough set of designs that the client can get a general idea as to how the site will function and operate. It is by no means perfect and helps me better understand the client's needs as well as get a "heads up" on what tools I'm going to use to satisfy their needs.
Once we have a set of roughs done, I use Adobe Illustrator to make a black and white set of wireframe prototypes; these are iterative and allows both myself and the client to get a bird's eye view of what the site will look like from a functional standpoint, and serves as the "design bible" that everything going forward will be based on; font choices, colors, layout, etc., are all defined here.
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