I saw a post in an off topic part of a role play game forum I was part of. Someone had posted a message to give them suggestions of something to do whilst they would be away from our game on holiday for a while. Geocaching was suggested, but nothing more was said about it, so I did a Google on the suggestion and it kind of went from there.
A few days passed before I had a go at finding one. Used my better half's car satnav for the first couple, and then my interest really grew.