Whether or not you have a microphone, you`re going to have to be creative with your language. However, the language will totally depend on the the other person. Maybe she will want you to use explicit language, or maybe she prefers something more romantic. Feel her out first.
Start off by asking her what she`s wearing, then describe what you look like. Then converse back and fourth. Let her start the fantasy, then you continue it until you both end up having sex.
A lot of people feel that masturbating to a computer at first can be ridiculous, but it actually can be a great experience. If she can`t see you, but can hear you, breathe heavily on occasion to let her know that you`re really into it.
If you don`t have a cam or a mic, rather than masturbating with one hand and typing with another, take turns. Let her write while you satisfy yourself, then after you orgasm, you do the writing while she gets off.
Some things to keep in mind:
1. Remain anonymous
2. Don`t make a habit of it
3. If you surrender yourself to the fantasy, the other person can be anyone you want.
4. Have fun!