If you mean like leaves on a bead (rather than beads shaped like a leaf), make your bead, take a stringer and head the end up until you get a tiny gather, then press it down on your bead, a proper firm press so the hot glass smooshes out, then (and you got to be quite quick), pull your stringer downwards (whilst still pressing into the bead). Hopefully you'll have a vague leaf shape- if you heat it too much it will end up like ablob though, so as you heat press with a marver to stick the whole shape to the base bead. You can also press the middle with a razor tool for a vein-crease down the middle.
See classy paint explanation:
