3 Tips to tell if an interior wall is load bearing

1) Look at the ceiling above and see which way the joists run. If the joist are running parallel it's non load bearing. If the wall runs perpendicular to the joists it might be load bearing.

2) Look at the dimensions of the house to help determine which way the joists run in the case where they are not easily visible. On a rectangular house the joists would typical run the widthwise not the lengthwise.

3) See if you have a gable roof. The load bearing walls run parallel to the ridgeline.