Assuming you are referring to graphic design and not product design, this is how I work with a graphic designer friend on all my apps. After many iterations, we

Assuming you are referring to graphic design and not product design, this is how I work with a graphic designer friend on all my apps. After many iterations, we've found the method that seems to work best between us is that I code up a functional prototype and then we have frequent intense on-the-spot design sessions with a lot of back and forth. This was initially quite unnatural for my friend, who preferred doing elaborate design explorations on his own, but we now agree this new method works best. The reason I like to work like this is because until I work out how the software use actually flows, it's pointless to make it look shiny. And working out that flow itself is a rapid iterative process, which changes the UI many times over. I hate to make my friend design stuff which I will then throw away the next day, although some of that is inevitable. Over time as the design gets clearer, we work out a visual grammar of sorts, which I can then just draw from as I build more features. See http://giniji.com http://giniji.com for an example of a work-in-progress.