You should pay attention to the people around you. You should know the number of people around you and their location and distance from you. This is obviously easier with fewer people rather than more and I don’t necessarily expect everyone to be able to be constantly aware of the exact number and composition of crowds of hundreds of people. What is especially relevant are those who might harm you. You should pay attention to the body language and facial expressions of those you can see (see post on Body Language). You should also be aware of animals which might be a threat. Generally this means fairly large animals (this can vary, of course, as some small animals (e.g. certain spiders) can be quite threatening). For the most part, body language applies to animals as well, though of course the language / dialect is different.