Hmm, well, Use your imagination. It also depends on what you'd be comfortable doing.
There's quite a few things you can do / try to liven up your AB time. Combine some things, pretend, play and talk with your plushies, watch cartoons and "talk" to the TV... just let your mind run wild.
I agree with Lukie, there is so much you can do but it's all about you and your personality. For me I'm a very girly girl and I like talking to my plushies and having tea parties. I also like to curl up with my blankie and watch movies or play dress up. So just be creative and have fun, thats what its about.
The best thing to do is try to pretend you're a baby or toddler or whatever your fantasy is, then act accordingly. Get so into the role that you think it's real. I've done that without even trying to when cross-playing in online RPGs (playing and acting as the opposite gender online), to the point where I was uncomfortable sitting at my computer shirtless, because I felt that girls shouldn't be topless like that. I'm not transgendered or a sissy, but it was a very fascinating experience. For a short time, my subconscious was convinced that I was female. If you can achieve the same thing with your AB fantasy, you'll have an incredible time.