I'd have to go book hunting in the basement to get the information on alignment by string method.
One method that I've used on level ground to get a ballpark toe measurement on the front end is by...
Raising each front wheel so that you can rotate it by hand.
Take a crayon/chalk piece with a fine point and hold it steady against the tire as you rotate the wheel. You could also hold a square on the pavement close to a tread line that runs the circumference of the tire to see if it is unchanging in position as the tire rotates. If unchanging, than use it as a reference point.
Having let the tires back down, get in the car and drive forward and back once or twice to get the suspension to settle and the vehicle driving in a straight line.
Shut the car down and put on the ebrake.
With a friend, have them hold one end of measuring tape centered against the line on one tire, while you take the measurement on yours, from both front and back - as if the tire is rolling towards and then away from you.
Compare the measurements. If the front measurement is larger then the rear, you have "toe-out". If the rear measurement is larger than the front, you have "toe-in".
In place of a friends helping hand, you can make a simple templet out of three pieces of plywood. I noted this from the same book I believe that discusses string alignment.
You need a main board length that is as long as your overall wheel track minus 1/2 tread width. You then need to securely affix a pointer board that's say as tall as the tire's radius. On the other end of this long board you need to securely affix a flat piece that again is as tall as the tire's radius, but also as wide as the tire tread. Paint the ends of both the pointer and recorder board white so that markings show up clearly. Mark a line on the pointer board for which alignment will be set, and leave the recorder piece for marking the positions of the scribe or noted identifier on the tire, with pencil.
Using this board, one can simply lean it up against the tire so it doesn't move, set the pointer end, and walk over to the other side and mark the recorder board face, making a notation of "F" or "R" to identify from where the measurement was taken. Repeat for both the front and rear of the tire. A quick glance will easily tell you the toe condition, and you can quickly measure the difference with a short ruler.