A lot of learned coping skills.
Always put your wallet and keys in the same spot.
Use timers, alarms, calendars and to-do lists.
Write everything somewhere. Make this as simple as possible, otherwise I can't find what I wrote when I need it.
Make your environment as appropriate as possible to the task you're doing. For me, this usually involves going somewhere else, because otherwise dealing with the chronic mess becomes the distraction by itself!