Broadside - let the near leg clear forward and use the opposite leg for line of site. This offers an unobstructed shot to the vitals.
Quarter Away - again use the opposite leg as the line of site and drive her home.

These are your best shots on a bear with a bow. While the others can be done they are risking due to the large shoulder area of a bear. A liver shot bear will die but is not much fun to track...so quarter towards are very delicate affairs with bears and bows. One look t the provided anatomy link of a bear will show you all you need to know.

Aiming mid body on height will put you in the vitals.

Enjoy and good luck.