Move all furniture out of the room, if possible. Cover the floor and any remaining furniture with dropcloths to catch all debris from removing the texture.
Scrape the wall texture using a high-to-low movement. Be careful to not dig into the underlying drywall and glide the putty knife smoothly along.
Mix 10 parts of water with 1 part of trisodium phosphate in a bucket. Wear rubber gloves while saturating a towel to wet the orange peel wall and soften any areas not easily scraping off.
Let the TSP solution soak in for a few minutes and return to scraping.
Wait for the wall to dry and sand the wall with fine-grit sandpaper to make it smooth for the next refinish. Vacuum the dust with a shop vacuum as you sand to catch as much of the dust as possible during the removal process.
Prime the wall with paint primer before repainting, retexturing or wallpapering.