In the texts of the link I put in previously, they talk about aiming the sundial to the north, but what if you don't know where the north is and you don't have a compass or a map?

That's no problem, you'll do the following:

Wait for a sunny day and go outside halfway through the morning (nine- or ten-ish), taking with you:

Place the stick into the ground. It has to be 90 degrees, so use the plumb-line to check this.
The stick will cast a shadow over the ground, unless the day you've picked turns out to not be such a sunny day and it starts to get really cloudy, in that case, wait for the next opportunity)
Now place one of the pieces of paper over the shadow. This is the first step, you can now do something else till later in the afternoon, say four-ish.
When you look you'll notice that the shadow has changed it's position and will be about the same length as the pieces of paper.
Place the second piece of paper over the shadow.
Now connect the ends of the papers with the string or rope.
Find the middle and connect this with the bottom of the stick.

Congratulations! The line that is showing is your north-south line. you can now sit down, relax with a nice cool drink....don't forget the suncream!