I've been nudging my husband to take fencing lessons together for years. :)
Be straight and forward about your preferences. You'll be much more likely to find someone who meets the profile.
Oh, I am very straight forward about my preferences, since even if they're not into that sort of thing, it's still fascinating. A few have ended up intrigued enough to experiment (or I've goaded them enough to hit me), but many just wig out when they see me respond as if tickled or pleasured when struck.
I've only met one sadist in person, the rest took a lot of work to not feel guilty about it (again, goading helps). With enough work they can enjoy dealing harm, but there's always that sense of restraint that's just... disappointing.
Not sure if it's uncommon or just bad luck. From what I've read up on, female doms/sadists are less common than male ones, and male subs/massochists are less common than female ones. Guess I got the short end of the stick.
There's so many social norms that dictate that hitting someone is bad without having some form of justifiable anger. "Come on, hit me~" even after extensive explination just gives this weird expression. More often than not, I have to tease relentlessly to get even a sock in the shoulder during the earlier portions. Enough repititions can get them over that hurdle (usually ends with them hitting other people who tease reflexively, it's awesome), but so far it hasn't lived up to naturally sadistic tendancies.