In just about every situation you mention, I suggest the following:
1) Assess the surroundings - you're looking for distance or safety issues between you and the threat.
2) Identify your options - figure out which of the options are better for that particular moment such as Fight or Flight. Then look for escape routes for you and also for the threat's exit route since most threats are based on one or the other entity perceiving that they have limited options available to them.
3) Preparation comes BEFORE the encounter... look around the outside of an enclosure before entering, know the habitat of creatures likely to be encountered, park in well-lit areas if you're going to return to your vehicle after dark, don't irritate or engage people who are larger and/or appear unstable, etc.
Pursuing knowledge now is always preferable to learning too late... keep up the good work and think through some of the potential outcomes for the scenarios you describe and think about 'turning points' at which the opportunity comes to impact the final outcome... If I do [this], it could end [that] way but if I do [thus] it could end a [different] way.
<edited because my hands & brain function at different speeds
[This message has been edited by BuggabooBren (edited 03-05-2004).]