The idea is that a diesel engine will run only a dozen or so revolutions on a prime. The fuel must be in the fuel line and the needle valve opening somewhere about right to sustain running.
Ken added, "Once it is running, increase compression until there is smooth running, but do not over compress. The engine will stop. Better a little under compressed, than over. Also, close the needle valve for best running. A point of closing will be reached where the engine suddenly quits. Back up about ½ turn and that is the run setting."
Couldn't have said it better myself. Starting diesels is an technique that requires more "feel" than a glow. With practice, you'll learn when to back off the comp, when to screw it down, etc. Compression setting and needle setting are linked too. To make the engine run slow, back off the comp, but as this decreases the pumping action, you'll need to open the needle usually, or it will die. Once it's running happily though, just stand behind it and drink in the wonderful smell!