I use eye pins whenever I want to suspend a charm right beneath of of my creations: I stick the rod into the creation and use the rod’s protruding end to make a jump ring (in case the rod is too long, you can simply cut it to the length necessary to shape a jump ring). You then only have to mount the charm on it! It is easy!
I use head pins to suspend beads, e.g. from earrings. You just have to insert the pin into the bead and form a jump ring with the protruding part of the pin. (In case the rod is too long, you can simply cut it to the length necessary to shape a jump ring.) You then only have to mount everything on an earring blank!
I use this sort of clasp to close long ball chain necklaces! It is the easiest way to go and they avoid making inelegant knots! Pay attention when choosing the clasp size, it depends on the thickness of you bead chain.