For a great tutorial on friendship bracelets, I suggest trying this one from Honestly WTF:
This is how to do the chevron style, which uses the normal knot and the reverse knot. For just the stripe pattern, use the normal knot (the second picture of the tutorial)
When making bracelets, I find it easiest to do it at a table with the bracelet stuck to the table. It makes it easier to seperate your strings and keep count of your knots. It will look a little messy with your first couple of rows until it starts straightening out.
If you’re looking for some inspiration for colour combinations, I suggest trying the amazing Colour Inspiration posts from Creature Comforts!