peek in the attic or look at the ceiling carefully and determine the direction of the rafters. Once you determine the direction they are going, you can tell. This way works MOST of the time, and it works only for a one story home. Two story homes, I would definately say DO NOT DO IT REGARDLESS.
If the walls are perpendicular to the rafters (or going the opposite way), they are load bearing. If the wall in question is going parallel to the roof rafters, the wall is NOT load bearing. Now this complicates stuff if a non load bearing wall is connected to a short bearing wall, then the non bearing wall has bearing on stabilizing the bearing wall which means it should not be disturbed.
Removing walls in side a home really requires alot of study and feasibility. Think of re sale value, think of stability, think of insurance claims if you screw up and the house caves in. Think of the carpet or tile flooring that will be void in the area where the wall was. Think of the electricity in that wall that has to go somewhere else.