I normally fly shorter, non-stop trips, thus when my son just baaaaarely missed his connection I was caught off-guard as to what to do next. With his confirmation number and birthdate at my disposal I called the airline and obtained a seat assignment for the first flight out in the morning before he made it to the front of the queue at the customer service desk at the airport. Ultimately an all's-well-that-ends-well story. However...

What are the first three things one should do if you think you will miss your connection?
What are the first three (five?) things one should do if you missed your connection?
What pushed this miss connection over-the-top is he had to gate-check his bag on the first flight, thus wasted ten minutes waiting for his bag to be delivered to the jetway. Should he have abandoned his bag on the jetway with the strong assumption that ultimately it would have found it's way to the final destination (i.e., a $75 delivery fee would have been cheaper than a hotel room)?