Similar to the "chillies" thread - I'll give the same answer I did in that one: a liberal dousing in plain old washing-up liquid, rather than normal soap - lather it up good (lukewarm water is fine), have a decent scrub, rinse. But this must be done as soon as you've finished handling the garlic. Works equally well when having handled chillies, onions or fish. The residues from all these are oil-soluble and will be dispersed by washing-up liquid the same way fats and oils are. Rubbing the hands with cooking oil before washing will facilitate it but I find generally it's not necessary.
No need for bicarb pastes, lemons or bits of metal.