You can make a house seem larger by removing doors that aren't needed for privacy. A door that doesn't serve a necessary function can easily be removed in a few minutes. Unfortunately, you're still left with a frame in the wall that looks like a door should be there, along with the doorstops, latch and hinges. Removing these will leave holes in the casing and then your opening will look like it needs a door and hardware. The best option is to take the whole unit out.
Remove the door. Remove the hinge pins from the door by placing the end of your nail set on the bottom of the hinge pin. Tap the nail set with a hammer until the pin is forced out of the top of the hinge. Once the pins are out, you can pull the door free of the frame.
Remove the moulding around the door frame. Cut through the paint that joins the moulding to the wall with a utility knife. Many painters will use caulk to smooth this joint. Making a cut between the wall and the moulding will prevent damage to the wall when you remove the moulding.
Pry the moulding away from the wall and frame with a pry bar. Work carefully when using the wall as a fulcrum. Placing a flat piece of scrap wood under the pry bar can prevent damage to the drywall or plaster.
Cut through the nails holding the frame to the wall with the reciprocating saw. Door openings are usually built slightly larger than door frames to allow finish carpenters room for adjustments. If your door frame is wedged too tightly in the opening to allow room for the saw blade, use a pry bar to force the frame away from the opening.
If you need to pry the frame out of the opening, work from one side of the opening to the other. Start at the bottom of the frame. Pry the frame an inch away from the opening on one side. Move the bar to the other side of the opening and pull the frame out an inch from that side. Working slowly and methodically will prevent damage to the wall.
Wear eye and hearing protection while using any power tools.