I imagine the hassles you have with customs would depend on
(1) how high the local law level is
(2) how big the starport is
(3) whether you work for intelligence and they have a "deal" going.
The general rule here in the states is that when you file your flight
plan, you check the box labeled "adcus". Then you make sure you're
on time. "adcus" means "advise customs". Normally in the U.S. if
you're fair-weather flying (navigating by ground reference, good
visibility etc.) flight plans are optional. When you go accross the
border they are mandatory.
Canadian customs is great to work with. U.S. customs SU**S! They
are surly, obnoxious, and prone to charge you fines for failing to
declare your pet fish on departure. Almost all good-sized airports
in North America (the ones served by >1 commercial airline and near
a city > 100,000 people) also have a full-time and on-call customs
office.
In MT terms, then I call these class A and class B starports. They
*will have* customs. Otherwise, you might have anything you feel the
adventure needs. Special ops, duty-free ports, whatever.
Richard