Canada

A little wordy, perhaps a little too in depth, but a great article on proper aiming.

General rule of thumb:

Locate the headlight adjustment screw before starting, and see what tools you need to adjust it. A screwdriver is normally all that’s needed, but it depends on the vehicle.

Ensure the headlights are in low and not on bright/high.

Park on a flat level surface, with the headlights aimed at a wall approximately 25 feet away. Can pace it out, just needs to be close.

With a measuring tape, measure from the ground in front of the car to the center of the headlight assembly. Take that measurement, and subtract 2.5 inches. (Eg, 30 inches now becomes 27.5 inches.)

Head over to the wall, and measure from the ground to the center of the bright spot the headlights make on the wall.

The bright spot should be at 27.5 inches as per your measurement.

If not, open the hood and locate the headlight adjustment screw. Turn the screw, one direction will raise the light and the other will lower it. Turn the screw until the bright center of the light is at the correct height (27.5 inches in this example). Repeat for both lights.

This will get you close enough 99% of the time!