The way I generate 'missions', basically one-shots, is write down a number of different buzzwords (NATO, Warsaw Pact, Food, Tank, Bridge, etc), about 20-40, and throw them into the
list randomizer on Random.org. I take the first 4 buzzwords and work out the details from that.
Pretty crude, but it gives a pretty good base from which to work off of. Here's an example:
Weapons
Radiation
Bridge
Convoy
The locals want to raid some long-abandoned Warsaw Pact/NATO caravan that is rumored to be filled with weapons, and is sitting dormant on the local bridge. But little do they know, the vehicles had passed through a hot area, and are still baking with radiation. The bridge also needs to be cleared for better trade traffic. What will the PCs do?