Modeling

Before you start, make sure you understand all of the wall's functions and know how well they can be served when it's gone.  Check to be certain that the space the wall divides will not seem ill-proportioned without it.  Note that besides serving as a partition a wall may carry pipes, wires or heat ducts.  Keep in mind that although removing a wall may join two spaces together it does not actually add any more space than the few square feet in which the wall stands. 

To size up the job, look the wall over.  The number of outlets and switches will suggest how much wiring lies inside it.  A bathroom directly above may be hooked to plumbing that goes down through the wall.  From the basement you may be able to detect whether heating pipes or conductors rise within the wall.  

If all you find is wiring that terminates at outlets in the wall, you can remove it when you break the wall.  A hot-air duct connected to a wall register can be cut back to the floor and capped with a grid.  Even if you encounter many pipes and cables, you may be able to remove the bulk of the partition and leave part of one end of the wall to carry the various conductors, which can be moved there by a plumber or an electrician.  

More critically, you should be aware that the wall may bear weight from above, thus serving as a vital structural element of the house.  If it does, you will have to limit the width of the opening to 14 feet, because a bigger span entails too many risks and difficulties.  To replace the weight-carrying function of the wall, you will have to install a visible overhead beam, as well as end posts for this beam that may also be visible, so that instead of removing the wall without a trace you make an arch.  These intrusions can be minimized by surfacing the structural members with wallboard to match the walls, or by positioning furniture, such as bookcases, to hide the posts. 

The key clue to a load-bearing wall is joists crossing its top plates perpendicular to them.  You may be able to see the direction of the joists from your attic; you may have to cut a peephole in the ceiling next to the wall to be removed.  The basement can also yield clues.  If you find a girder or a wall running under and parallel to the partition in question, you can be quite sure that the partition carries weight down to this support.  If any doubt remains, assume that the wall bears weight. 

As the converse of a load-bearing wall, a nonbearing wall usually runs parallel to the joists and perpendicular to the long walls of the house.  Walls enclosing small spaces like closets are probably non-bearing walls - but be sure to check.  Because nonbearing walls serve no structural function, they can be removed without leaving an arch.