I have looked at an L14-20 and an L14-30 receptacle, which is the same as on your generator. They use the same wiring sequence.
#1 should be ground
#2 should be a hot leg
#3 should be neutral
#4 should be the other hot leg
*****Please verify yours are the same, by looking at the sides of the receptacle on your generator*****
Gold screws are hot and silver is neutral - green is ground.
Some of your equipment may not be wired for four wire power. You may only have two hot wires and a ground. In that case ignore the neutral when you wire the plug on the equipment. The two hot leads may be both black or one black and one red. It does not make any difference which one goes to which hot connection.
If you are using 125 volt equipment you can chose either of the hot legs to power the item. One hot, one neutral and one ground (black, white, green).
*********If you have any doubt about which connection is which color (gold-silver-green) take it out of the panel on the generator and verify it*********
Another easy way, if you have a simple voltage probe is to test each port on the receptacle. A simple one costs about $2.00 at the hardware store to test one leg at a time. Only the hot ones will cause the bulb to light. (with the generator running of course)
I do not have a 50amp receptacle to check and see which is which. They are likely the same sequence as the smaller ones, except the U shaped port is probably the ground. Again, you should be able to see what color wires goes to this receptacle and see what color the screws are.