The low beam pattern needs to drop 3" over 25 feet. Measure from the center of your headlight to the ground, and subtract three inches. Find a level spot and park 25 feet from a wall, then mark the wall at that height with masking tape. The top of your low beam pattern needs to be just under the tape line. If you have sealed beams than the light pattern will be a "blob" of light that can make aiming more difficult- there won't be a defined line where the upper half of the low beam pattern stops off. If you have H4 headlights that are E-code, you'll have a sharp cut off on the top half of the low beam pattern that makes aiming easier.
Here's a diagram.
Here's a shot that compares the E-code pattern (left) to SAE/sealed beam pattern (right side). You can see that the E-code makes a sharper line for easier aiming, and less glare for oncoming traffic.
