First Motion Procedure

Plug in one motor at a time. Turn off power between plugging in motors, and hit reset immediately if motion is incorrect.
Plug in the X motor. Plug in the X endstop with green facing right. Note that all the endstop plugs have green facing right.
Move the x axis manually to observe if the axis hits the end stop. The end stop should light up.
Move the axis back away, and hit Home X in Cura.
If anything goes wrong, hit the reset button.
To correct direction of motion, reverse the plug on the RAMPS
Label the RAMPS plug with the wire color that is at the top of the RAMPS board. This will assure correct orientation of the plug if it is unplugged later.
Connect the Y Left axis.
Move Y left slightly to see if it moves properly. Reverse the plug if it doesn't. If there's an issue - check 3 things: check connection, wire order, or reverse the plug on RAMPS.
Disconnect Y Left and label with the wire color that is on top.
Connect Y Right - see if Y right moves correctly. Troubleshoot as before.
Once Y right moves correctly - label it as before - and reconnect the Y Left axis
Move the Y axis by hand to make sure it hits the end stop. Hold one hand on the reset button - then home Y in Cura - and reset if anything goes wrong. Troubleshoot as needed.
Now validate the z axes, one at a time, in the same fashion as the Y axes. Plug in the Z probe with green facing right. Note that Z Up means bed going down.
Verify that the Z probe is approximately 4 mm below the tip of the nozzle.

Troubleshooting

If motor chatters instead of moving, verify that all 4 pins of the stepper motor Dupont connector are inserted onto the motor headers
If motor chatters instead of moving, verify that the wiring order is the same on the stepper and the RAMPS connection

Once all motion has been verified, it's time for the extruder and heatbed.