I always park vehicles by doing the following:

1. hold down the brake pedal
2. shift to Neutral
3. set the parking brake
4. release the brake pedal to let vehicle roll a bit
5. shift to Park.
6. turn off engine

I thought this would prevent the automatic transmission's parking pawl
from becoming wedged, but after driving my father's 2002 Nissan
Frontier 2WD w/automatic recently, I think I may be wrong,

I had no problems the first time I started his truck, but on the
second start and afterwards, the shifter would stay stuck in Park
unless I moved the truck back and forth slightly.  This happened every
time until I decided to adopt my father's method of parking:

1. hold down brake pedal
2. shift to Park
3. turn off engine
4. release brake pedal (truck usually roll some)

I never had any more problems with the shifter being stuck, but why?
Also this never happened with my 1998 Frontier 2WD automatic.

I don't think the neutral safety switch or any brake-transmission
interlock is to blame, but I'm no expert.  The parking brake on the
2002 Frontier held fine, both forward and backward.