Where do I look?

I am blessed with this problem of not knowing how to cast or hold my gaze in certain social encounters. This is what I usually do :

Scenario 1 :
Encounter a stranger. Likely place - lobby of an apartment. Glances meet, they dart away after a brief smile and then eyes are again lowered. Thereafter, I ignore the person and study my feet or if waiting for the elevator stare at the floor numbers being displayed. Alternatively, I have the unfocused look that does not focus on any thing particular but somewhere above the head.

Scenario 2 :
If the situation demand that both and the stranger you are circumstantially waiting for something for a long period of time – at clinics /tubes station/bus stops/ or traveling in public transport then there will be occasional glances from both sides – may be a brief smile or a nod. The there is definitely the checking out of your corner look.

Scenario 3:
This one happens to me often and it is the worst. The person is familiar but not an acquaintance- perhaps lives in the same apartment, walks down the same road or goes to the neighbourhood shop. You spot the person at a distance and dread having to acknowledge. You must do it at the right time. If your glances have locked and smiles have been exchanged too early then you have the problem of not knowing when to break it. The worst is when your glances meet and then you smile holding the glance until you suddenly drop or shift your eyes to break it. Ouch! It is so awkward.