I just finished up a long term project that floated in the fuzzy soupy place between a phased waterfall process, and a seat o’ the pants agile endeavor. The project was definitely not agile, and it was definitely not waterfall. I feel like we (TBG) are going to end up in that spot quite a bit, if not always as we try to push the needle further towards agile. Here are a few things I learned from a designers perspective that I don’t want to forget any time soon and should probably think about more…

1. Its okay to do design up front – Early visioning and exploration is invaluable. Put some time constraints around it and go nuts. Having some semblance of where the “thing” might end up is helpful for everyone. Just be sure to always remind yourself, and everyone else, that you are probably wrong this early on. 
2. Be reductive – Your devs will buy you more beer. If the goal is agile, and everyone wants to work that way, as designers you have to inflate your reductive filter to an uncomfortable size. After early visioning resist the temptation to make your designs anymore complex than the bare minimum. Figure out what your thingy/widget needs to do baseline, and start there. Why? Because your homey next to you has to build the damn thing, and you don’t get to refine it until its built, at least you shouldn’t.
3. Rally around the build – As designers its easy and natural to go down a path of iterating and refining a paper version of what you want to make. With agile, this can create two very sepearte tracks. Developers and their build, designers and their documents. Inconsistencies between the two tracks, and failure to meet unspoken expectations are the result. At that point you are part of the same team but your not working on the same product. To fix this designers and devs should be rallied around the same work product as early as possible. Camaraderie  goes through the roof and the reward of iterating the actual build will make you tingle.
4. Whenever you can, get your hands dirty – On this particular project things really started swinging when designers were writing CSS here and there and generally focusing on the build more. Nothing bridges that gap between designer and dev better than dusting off the old markup books and diving in. If you’ve got the chops, do it… If you don’t, consider dabbling.