Pins are labeled directly on the connector. In tiny tiny numbers. "Left" and "Right" are arbitrary notions to a connector system that can be either male or female and can be viewed from either side. Always go by the numbers on the connector itself so you can be sure.

Trial and error isn't really needed, no. It's just that I never remember which is which so I just mess with it until it works.

For example:

Connecting PC serial port to empeg main-body-casing serial port: Crossover cable needed.
Connecting PC serial port to empeg docking sled serial port: Straight through cable needed.

I don't know what the port is like on the handheld device you're planning to use. Is its port designed to connect to a host PC? If so, it might be crossed over already and therefore would need the opposite cable of what a PC would need.

So:

Connecting unknown device X to empeg serial port X: ? Cable required?