tools needed:

Lazer projector($20 at Canadian tire)
Straight edge mount(4" aluminium channel 20" long)
7' long ruler(I used a 1 1/2 s/s angle

Make a base line on one end of the ruler and cut a piece of angle with a slot which will serve as the marker at the measuring end of the ruler. the ruler should be 12" up from the ground using a foot stool or the like.

The following is for a rear tow adjustment:

Set the ruler directly in front of the front licence plate, up 12" off the ground. At this point you can measure the distance between the rear wheel center and the ruler(aprox. 11'). Now take a second measurement from the rear wheel center, towards the back of the car. This is where you will position the ruler for the rear measurement comparaison. Starting with the LR wheel, aim the lazer forward and level, and align with the base line on the ruler(It saves time if you have a buddy moving the ruler for you). Once that is done move to the RR wheel and aim the lazer forward and level. Clamp on the marker where the beam is projecting(see pics on first post). It's now time to move the ruler to the back of the car, at the 11' mark previously determined! Still at the RR wheel, turn the lazer around, projecting to the base line on the ruler. Move back to the LR wheel and aim the Lazer rearward to find how accurate your tow is.

Parallel adjustment is a rear wheel tow adjustment. Have you ever seen a car going down the road sideways(crab steer)? Now that you know your rear tow is correct, it's time to determine if the rear wheels are going straight down the road. Starting at the LR wheel, aim the lazer forward and level. Using a measuring tape horizontally to the center cap of the front wheel, note where the lazer lines up on your tape. Perform the same measurement on the other side. Both measurements must be the same. A heim joint toe link set up makes this task a breeze!

The pic below shows the vertical beam projected on the garage door in the background. This is a real easy way of figuring out your camber angle.

It helps if you have a strength in geometry or have a carpenter background

Oh, BTW, as far as accuracy of measurement, it's not just good enough, it's bang on everytime!