How do i messure a RJ232 Cable

[FireStriker]

Im a very fresh newbie, Been watching EEVBlog for a while but just got my first muiltmeter 

I would love some tips and tricks but i have some questions in relations to measuring stuff for my Logitech racing wheel that im remaking a cable that would of come with it when it was new.

When measuring voltage on a connector, for example something like a USB plug (which i know the pinout off the top of my head), how do you measure voltage?
I would guess that you touch 1 Pin with the red probe and COM would go to ground.

This cable would go from RJ232 to USB and i want to double check pinouts and voltages so i dont fry anything.
So far pin 5 is Ground which is correct to the pinout im using to recreate this cable but for the rest of the pins im so fresh i dont quite how to figure them out, like confirming Data + and Data - as well as the power line.

Chris

[TheHolyHorse]

The best and safest way would be to use the summing (resistance measurement with a beep) function of your MM and measure each pin at each end of the cable. If it beeps or just show the value in ohms they are connected.

No need to connect it and measure voltages.