Hardwood flooring typically is installed perpendicular to the direction of the floor joists and parallel to the longest wall in the room. However, you may have to choose one or the other as the length-wise direction of the flooring boards. Which direction? If the subfloor is relatively solid, such as 3/4-inch plywood in good condition, you can install the flooring parallel to the joists. If not, consider adding subflooring to strengthen the base. This is not as critical with 3/4-inch solid hardwood flooring as it is with thinner flooring materials.
Professional hardwood flooring installers rack boards for easier installation. That is, they (or an assistant) place boards in position where they are easy to move it into place with a foot, then fasten. The boards are selected and racked based on length and color or grain.
As additional rows are added, make sure that the end of a board is at least 2 inches from the end of a neighboring board. Besides making the flooring stronger, it also looks better when the ends are farther apart.
To change directions of the tongue-and-groove in a room, or to join two rooms with opposite t & g directions, install a spine in the grooves between two facing pieces.