When I hit a dead period, I often pull out some old material and try to re-write.
Or I re-mix some old material - just to get the juices flowing.
Sometime, going to a different instument, helps unlock something.
I spend a fair amount of time (and cash) at used book & CD stores - and as a result I have a large backlog of music I have not listened to - (or books about various artists) often this helps me get inspired.
There are so many incredible recordings featuring great spngs and great performances - I find it hard not to get inspired when I listen.
Mostly I just keep writing. Sometimes it's crap (I know it's crap as I write it), but I feel a good writer not only has to write continuously, but should be able to write on demand.