Actually I can't really remember. It was probably a box of miniature plastic soldiers I saw when I was 12 (can't remember the brand) and watching Ridley Scott's The Duellists (Hussars!), but it was very casual until earler this year where I read a small book on Napoleonic warfare, then bought another one about Waterloo, and so on and so forth. So I'm right in the middle of learning everything about this period. Before that I was always interested in 18th century warfare, American Revolution, that sort of thing, but Napoleonic era is something rather new for me.
As for wargames I've been playing them for years first on paper and then PC but I was always a WW2/Modern/Classical (especially greek, pelloponesain wars) fan before now..