>>ferros+hz
Well, don't
stare at them. You know in advance that your contact will be walking down Merriweather Lane at 11:30am. If his shoes sport a single "X" near the bottom, that means the dead drop has the microfilm ready for pickup. If it doesn't have that "X", then try again next Tuesday.
If you see two X's in his lacing, the package is at the alternate drop site.
If he has 3 X patterns, you're burned! Make your way to the safehouse after losing any potential tails.
Glance quickly, agent, and keep moving.