Find 2 earrings which used to be a pair but have now lost their other half. Alternatively you could use a pair of earrings you don't like very much.
Note: They need to be dangley earrings not studs.

Using a pair of scissors or small pliers prise open the ring that the body of the earring is hanging from. Leave the ring open.

Now select what you'd like to hang on your new earrings. I've got tons of beads that I've collected over the years so this was tricky :).

Now put your chosen things/beads on to a small piece of wire. I used sandwich bag ties with the papery bit stripped off. You need to thread your first item all the way through till its in the middle then fold it in half and twist the two wire bits together. Thread your other beads on leaving yourself and little bit at the end that you can turn into a loop to hang from your earrings.

Do this with both earrings then fit the open ring from the old earings through your little loop on your new earrings and then using scissors/pliers close the ring up.
Ta da new earrings at no cost \o/