i have not yet seen anyone mention:

#1) paper tickets

e-tickets still require that you stand to
get the darned things converted to paper,
so that you can use'm on another airline.

if you already have paper tickets, the whole
exchange can usually be arranged over the
phone and you only have to show-up at the
gate of the other airline.

#2) carry-on bags are always a good/better
idea

#3) ask agents to check flyfo (flifo) for
flight info - not the swill in the resv
system.

-doug