Proper procedure is to make all connections unenergized, inspect the entire cable / connection run and only then turn on the circuit breaker for shore connections ( shore in this instance means an installed electrical service point )
For generators there is an extra step. After making connections its important to test the service voltages between all legs and the legs and neutral+ground. Large generators can be set up for a variety of industrial loads beyond the usual single phase / three phase 115/208 VAC we are used to.
We for many years had an exceptional special event generator vendor who always sent a trained operator for set up instilling a lot of confidence in all of their customers. One event came up in which our customer hired a generator from a new supplier but assured us that a trained operator would be on hand. Come set up morning - in the dark of course - we provided tails and let the get op do his thing. Started the first chain motor and it moved all of about two feet and poof a bit of magic smoke came out. I checked the front of our PD and all three of the voltage meters were dead. I ran down to the generator and asked what's up. The Gen op said its all good here. I looked at the meters on the genny and found it was set for 460 VAC. The "trained generator operator" turned out to be simply the truck driver.
Trust but verify.
Pat [ or perhaps "the PatS" ] were the absolute best ii've ever worked with. The only time using a genie that you could just 'forget about it'....