What is the procedure for checking the headlamp alignment as part of routine maintenance?

Its actually fairly simple. If its on your own vehicle, you can tell on a dark road with your headlights on if they are pointed out far enough and aligned (you will see light ahead the same distance on the left and right side.

In a shop pull in and turn on the headlights pointed at the wall. About 10-15 feet back from it.

Look at where the head lights hit. It should be level. If its not, figure our which one needs to come up, or which one needs to go down. Pop the hood and look at where the headlights are installed, there is typically an adjustment screw you screw in or out to raise (its usually like a thin rod with a screw top right next to the light)

Turn it and watch the wall to see if its bringing it up or down and continue until they are aligned.

Then hit the road and make sure your distance is where you want it.

Good Luck!

As part of ROUTINE maintenance? The way I do it is I pay attention to how the headlights illuminate the road. If they're pointed the right direction, you can see well with them and you don't blind the driver ahead. And as long as you don't run into anything they stay that way.

Need a flat vertical surface like a wall or garage door and turn the lights on a measure the distances between the headlights on the car and distance from the ground and then the light spots or beams on the wall or garage door. Move the headlights until your happy.

Or you can buy a suction cupped tool with bubble levels and make adjustments until the bubble levels are where they should be. 

It is such a PIA that it only gets attention upon request. You shine the lights into a wall and measure. Most times nothing is wrong. It is the operator.