I was trying to do the same thing with my boyfriend, luckily for me it's working so far hehe

I just did little things though... try things like kneeling on the ground when she's stood up - it's a little thing, but it does make a weird difference :P
Remember how she likes everything, like how many sugars in her tea, or what her favourite meal it and make sure she's always taken care of by you; just act like you're her submissive already when it come to more everyday aspects of your relationship.

There's always little things like saying "Yes Miss" or something along those lines when she asks for something, but in a jokey way - she'll either tell you she thinks it's strange or like it, or just laugh along. Just saying things or doing things in a jokey setting is sometimes the best way, like Icey's idea of the costumes - because it can all seem like harmless fun to her, or she'll enjoy it, but it can all be done without the fear of freaking her out