These are some that I have made so far, and one in progress. I made others some time ago, but I can't find them. I have know how to make friendship bracelets since I was in high school, which was eons ago.
Click on the link that will get you to a site that gives instructions and patterns.
Once there, click on basic knots for a tutorial with pictures.
It may be useful to those who already know how to make these bracelets. My how to is for others in simpler terms.
For the basic knot tying, start with however many colors and number of strings you want at about 60 inches long, fold in half and tie in a knot.
The more strings you have, the wider your bracelet will be.
Start with the first string on the left, hold second string while tying first string around it as shown.
Tie the first string a second time around the second string, pulling the tying string straight up.
Do the same using the tying string around the third string.
Continue tying until you get to the last string, so the first string will become the last. It will slant naturally, so if you want it to go straight across, now is the time to straighten the knots. The second row of knots will then lock them into place and the remaining rows will then be all straight.
Once you have tied all the colors in the bracelet once across, it will look like this. Repeat steps 2 through 5 to continue to length of your bracelet.