Get in the mood
Set the scene just like you would for any night of passion: light some candles, get undressed and find a comfy place to dial up your sweetie. Even phone-sex operators don't just launch into x-rated dialogue, so once you've got your lover on the line, casually transition your usual chit-chat into pillow talk. A good way to start is to express your desire to have him or her with you, or by evoking the memories of an especially passionate romp you've shared before.
Use your knowledge of your partner's particular turn-ons to create an unforgettable mental image. Tell him or her what you're wearing (or not wearing), what you imagine your partner looks like (focusing on your favorite body parts) and what you'd like to be doing to each other to paint a vivid fantasy.
Get your partner to confess his or her most carnal desires, too, by asking questions. Example: "Would you like to touch my...?" You'll not only learn about what's arousing your partner most, but you can also subtly direct the conversation to suit your desires, be they kinky or romantic.
Take matters into your own hands
When things really start to heat up, don't be shy about lending yourself a hand. Don't even think about not playing out the fantasy to its natural conclusion! Encourage your caller to tell you where and how to touch yourself and be graphic in your descriptions of every sensation.