Random notes on tailing people:
If you're following someone in a
crowd, don't stop when they do. It creates a dead-obvious
deer in the headlights effect, because you'll never be able to figure out what needed to be done at the same time as your
target. Keep going with the
flow of people and stop a bit below them...they'll catch up sooner or later. Don't turn your back suddenly if you're spotted: chances are the target won't know you're tailing them, unless you act
nervous. Focus on the
person, not their clothes or other superficialities: they might take off their
coat or
hat.
All I can think of right now...