I would agree that working these out can be tricky.
The data sheet normally shows which contacts are switched when you push the plug in, or simply use a bare plug and a meter.
If you aren't using a PCB and are using something like stripboard, you can bend the lugs so they sit flat and mechanically stabilise them with solid wire straps or via pins.
I know these plugs and sockets are widely used, but I don't like them.
The important thing is to get the right sizes as the pin diameter can be different.
They rely on contact spring pressure to force the pin into contact with the socket sleeve and some are pretty sloppy.
There are decent power connectors available and for critical applications, I always change them to something better.