servo motor with AVR microcontroller

I'm about to build a 3 DOF robotic arm using servo motor. i have no experience using servo motor. so i need to know more about the following:
1. how to interface a hobby servo motor (3 wires) with an Atmel AVR microcontroller.
2. what is the algorithm ( or even better, the C code) to drive the motor shaft a known no. of degrees.
3. what circuit simulator software has a model for the hobby servo.

Use Google, this information is out there and covered exhaustively, including code.
Hobby servo signal - Google Search
AVR servo controller - Google Search

You don't need a model for a hobby servo it's a closed system there's nothing to model pracitcally. If you want to know how it will perform in your application you need to test it.