How do you get dread beads to stay on your dreads? - Dreadlocks FAQ's
It's all about finding the right dread for the bead. Very often, as your dreads mature the tips will become slightly fatter than the rest of the dread. Dreads like this are ideal for beads. You want to try to find a bead that will slip over the large tip with some pulling. If you can get some of the hair through you can often pull on it to help the bead get past the wide part.
Once it's on it won't slip back easily. When you slide the bead up higher on the dread it will generally move pretty freely. This is ideal. Each time you wash your dreads if you leave any of the beads on you want to be sure to slide them up where they are not tight. This will allow the dread under the bead to dry properly. If the bead (or anything else for that matter) is left tightly on a wet dread it will slow the drying significantly and it can lead to dread rot.