I don't know the details of anyone's specific strategy, but in general, you start with an educated guess (might involve a lot of the factors you highlight) and

I don't know the details of anyone's specific strategy, but in general, you start with an educated guess (might involve a lot of the factors you highlight) and then you monitor how people respond with bets. If more people are betting one way then the odds shift to encourage betting the other way. This shift is no longer really based on factors other than "as the house, we must come out ahead after the winners are paid".