Here's what you need:
Beads, clasps (4) and spacers.
elastic bead string ( I used 5mm and it was too thin. I had to double it.)
A watch kit (get them in the beading section of your craft store)
Layout your beads. You might want to switch things around a bit, so give yourself some time to ponder it.
Cut your elastic string extra long. (I learned this lesson all too well. I tried to skimp on the elastic and ended up with everything coming loose several times. Waywardness!)
Start with a the bead that you will put between the clasps. Create a knot that will hold this bead in place while you thread. You could also use an alligator clip.
Then just thread your beads in order, down one side and up the other. If you are using spacers, mark where they will go on the opposite side when you thread it on the first side.