Ooo..spanking is always fun for me
there is just something about seeing a butt jiggle slightly after a sharp smack, nothing too hard, though. Then again, i'm just intrigued by the female body, so seeing any part closeup is a pretty good turnon, but there is just something about the butt and curves and shading and sensations and..oo, gotta go find my gf..
Ok, back, Anyway, if you want to broach the subject, just ask, if she's over 20, chances are she'll have had a bf or something that smacked her butt and she'll either have liked it or not. Try playing around, most women are a bit more adventurous than men give them credit for...
Just try not to get too carried away unless she keeps asking for more or you discuss it first or there is a safeword. I had a really kinky gf that LOVED being spanked with a hairbrush until she was pretty well bruised. Was kinda odd doing it at first, but after watching her cum from it, I kinda got the impression she liked it
So, just talk about it, don't just snatch her over your lap and start wailing on her cute little butt...