I noticed how all the PWM functions in Arduino are all preset.
You just type in howfar you want a servo to go and it works.
Is there also a way to do this manually?
PWM and servo control are two different ideas from the Arduino perspective.
The PWM pins on the digital side allow you to control the duty cycle of a fixed frequency on select digital pins (3,5,6,9,10,11)
The Servo control activates the built in timer functions on Pin 9 and Pin 10 to allow precise 1.5ms to 2.5ms pulse train to be sent within the 20ms frame servos require.
If you want to change the PWM frequency, see this post:
Arduino Diecimila and the Atmega168: Changing PWM Frequency on the Arduino Diecimila and the Atmega168]/url]