Hey Bart,
I've successfully done this a few times where its lead to full blown phone sex. Basically, what it comes down to is being really flirty and creating a lot of "open loop" innuendo. Keep in mind that in order for this to really work well, you have to have already built some measure of attraction with her.
So I might say something like "So... what are you wearing?" in a mock sleazy tone to try and be funny. Then the girl will typically reply, either honestly or "play along" flirty. At this point, you can transition into highly VISUAL talk about what would happen if you were there with her.
(Keep in mind, if you're talking to her on the phone, your voice is going directly into her ear and it can be very powerful!)
So I might say something like "Mmmm, if I was there right now I'd be rubbing your shoulders and feeling how soft that little cotton shirt you're wearing is," etc. And start Escalating from there by describing in as much detail as possible physical and visual sensations. Say things like "What would it feel like if" and "can you imagine if" etc. can really begin to get a girl's mind working in the way you want it to.
As far as building anticipation goes, after you get the girl feeling good or get her aroused, she'll usually say something like "man, I wish you were here right now." And you can talk about how great its going to be when the two of you finall do get to hang out.
Other methods of aniticipation building involve you future projecting. So saying stuff like "We're going to have so much fun tomorrow!" or "I've got a surprise for you, just wait until you see it" can be very powerful.
Hope that helps,
Thundercat