Personally I think it's best to be up front about things rather than "roundabout," but to each his own. A surprise BDSM scene is probably not a safe BDSM scene (since it's good to plan/have a general idea of where things are going to go or at least know where each person definitely does NOT want them to go even though they're often heavily dependent on improv and anticipation/excitement/surprise can add to the thrill), IMHO.
I would say once you've been with someone for a significant amount of time they'd be more likely to try new things with you even if they aren't expressly "into" it to make their partner happy... for example with my Mommy I'd do anything she wanted to if I thought she'd like it because I love her and want to please her. Of course I'm a submissive, so I'm more open than a "vanilla" person, but...
If the girl isn't into any kink whatsoever it's just not going to happen. Some people just only like missionary, under covers, with the lights off and won't go beyond that. Personally I'd rather shoot myself in the head than go through that, but everyone's into different things.
But if you're in a "new" relationship if she IS into kink she may be antsy about experimenting because she doesn't know you quite well enough yet (BDSM can be quite dangerous it relies heavily on trust and knowing the other person, their bodies, their limits, etc). I'd suggest being careful with a "newbie" even if they are willing because you never know how it's going to affect them, if they'll get carried away, if they know how to take cues / be attentive of your needs/desires, if they can tie a knot without cutting off circulation... etc. Some people have a lot of baggage and/or pain in their life or even latent psychological issues and BDSM roleplay can be a shock to the system that will bring that to the forefront in a way they don't know how to handle if they weren't prepared for it. Of course some light spanking and very very uh... mainstream "kink" like furry handcuffs that don't even lock probably won't do that, but you never really know where a scene's going to wind up until you're in it.
But yeah... your best bet if finding a kinky partner is important to you is to look in "non-vanilla" settings or just be open and up front about your sexuality if you think things are going to head in a serious direction. Also if it's a relationship worth being in, your partner will be willing to experiment sexually if it makes you happy, but that's just my opinion. Now that being said don't expect a woman to go from missionary lights off to giving you an enema while you're tied up, whipping you 'til you bleed while it flows into you, and then wiping you down with baby wipes afterwards in one night... you've got to ease them into things and start them off with something that many vanilla people experiment with like spanking or gentle handcuffs / sensation play like pinching and nibbling and work your way up. Always be open, discuss what they liked / disliked, what can be done better, where you (both) want to go next, and research things you're curious about before trying them. Also I'd say know your partner VERY WELL before trying anything extreme / out of the ordinary. And I highly recommend never letting a stranger, escort, casual partner, or one night stand tie you up. I'd only let my Mommy (the woman I'm in love with) do that, personally... but a fuck buddy you know well could be OK, too. Just be smart, sane, and safe and you will have fun.