Some personal examples
I used to joke around with it to my girlfriend. Not like, "Oh, I'm gonna tie you up and tickle you!" But it would be more like me kidding around with her playfully.
2 very SPECIFIC examples. These are two of the best times I tickled my girlfriend without her knowing I was *planning* it. I use planning lightly, because I wasn't trying to trick her, but rather I put something new in a comfortable context so that it felt natural. I think that's key. Sorry for all of the quotes, but most of it is dialogue.
I started out with the bondage thing, like when I found out she didn't see Star Wars and I made a big deal out of it. I told her, "Well, I suppose now I'm going to have to tie you to a chair and force you to watch it." And then I'd see what her reply was. When she started playing along with these statements we progressed. She'd say, "Well, that wont help me like them any more." And I'd reply with, "well, I suppose I could find a way to force you." And things went from there. I *playfully* tied her to an ab lounger some days later and put in star wars. I poked her a few times by *accident* and pretended to be amused by her laughter. I told her that I wanted to hear her laugh, and I tickled her through the movie.
Another GREAT way that worked with her was playing dumb. Honestly. I would say something to the effect of, "I think I should wrap you in this blanket so you never leave" (something sappy). But before she replied I would then say, "But nevermind, that wouldn't be any fun, you would just lay there and not do anything. what would I do with you?" She'd reply with something like, "Well, you could tickle my feet." And I'd say, "But if you are all wrapped up, how would I get to them? You're not making any sense." Playfully pushing her away. She'd reply "No, silly, you could wrap me up but leave my feet sticking out." I'd pretend like she opened my eyes to the thought, and she'd go "uh-oh" as if she thought she gave me the idea. I doubt she thought I was that dumb, but still, like I said before, it put the bondage and tickling that was about to come in a comfortable context. One that both of us could enjoy without feeling outside of our comfort zones.
I strongly recommend trying to introduce tickling to your partner by allowing it to feel like a natural progression of events. And NEVER take it to seriously.
I'm sorry this is so long, but I have one more thing to add. Me and my girlfriend were not having sex. We were waiting for marriage, and so ticking for us was not a result of any sexual foreplay or anything.
Stevereeno gave some excellent advice, I suppose this is just some advice for couples that aren't yet active sexually.