Inside a joystick, there are 2 potentionmeters that measure x and y axis movement. You can refer to this as x/y pitch/yaw.. whatever...
This is the way the pins on a gameport are arranged (male)
Look at the chart on this site to see which pins relate to which digital/analog input.
Ok so this is what you do.
1. Find an old gameport joystick, or random db-15 cable with male connector.
2. Splice open the cable, and see which wire leads to which pin.
If you want to wire a knob that measures how far it is spun, you want to use whats called a potentiometer. These work like this...
If you connect the wire from the +V wire from the gameport cable to the center pole/lead, the other 2 leads will give you a variable signal depending on where the shaft is.
So if you want to use a pot...
3. Connect pot to cable. Refer to this pot as pN_x in code, where N equals the port number.
4. Wire up switches. You can put up to 4 for each port.
I hope this helped. Reply if you need more help.