The first thing anyone should ever do when deciding to make a change to their relationship outside of previously set norms is discuss it with their partner. Just springing something like bondage or spanking on your partner without her first-gotten consent could result in her pulling away from the idea if you startle her or her caling the cops for domestic abuse if she's not the open-minded, understanding type.

So, no, you don't just tie her up and wait for her to say "no f'n way." First off, if you surprise her like that, she's very likely to say it and double quick. First, you talk to her about it and then if she says no f'n way, then you know she isn't interested in the idea. However, if you tell her WHY this sort of thing interests you and ask her to see your point of view, then she is much more likely to be understanding of the whole process than if you just tie her down and go after her.

Another thing, it's not about being in control until you two decide to take your relationship to that point. You are not just suddenly dominant and submissive, you are just two people in a relationship until you have discussed or predetermined that your relationship will be a fetish based one or not.

Second rule of BDSM: Trust and communication are paramount above all else.