This old laundry area is about to become a shower!
When remodeling interiors you often have to remove existing drywall (aka gypsum board) to access pipes and wires behind it. Most people just put on safety glasses, dust mask, face shield, get a hammer and pry bar, and whack it to pieces. It makes a big mess. There's another way.
Step 1: Cut It Out
Start by marking out the area you want to remove and cut the drywall. Here I used a reciprocating saw blade held with a handle and at an angle to delicately cut the drywall without cutting into the wood framing behind it. I also cut a small notch around this piece of door trim that I was too lazy to remove.
Cut along any corners with a utility knife.
Remove any door or window trim, baseboard moulding, or crown moulding that may get in the way.
Also remove electrical cover plates, outlets, and switches. Plumbing fixtures will have to go too if there are any.
Step 2: Hunting Down Nails
Use a strong magnet like the ones found in an old computer hard disk drive to locate all the nails that hold the drywall to the framing. Mark the location of each nail with a colored marker. You can turn the magnet on its end to more precisely locate the nail (although this can miss if the nail is driven at an angle).
In US buildings the nails will probably be about 16 inches apart horizontally and 12 inches apart vertically. That's if it was built to code originally.
Step 3: Rip the Nails Out
Now use a small pry bar and hammer to remove each nail. Pound the pry bar into the drywall just to the side of a nail. Keep pounding and angle the pry bar to get underneath the nail head. Then pry out the nail.
You might find drywall screws instead of nails. If so use a screwdriver (or better a screw gun) to remove the screws.
Don't worry about digging big holes in the drywall. Just get the nails and screws out.
Start at the ones hardest to reach. Get on a step stool or ladder to remove all the higher nails but stop at the last row of nails above 4 feet from the floor. Then go up from the bottom stopping with one row of nails below 4 feet from the floor.
Finally remove the remaining nails. Be careful since at this point nothing is holding the drywall in place. Make sure it does not topple over onto you.
Step 4: Gently Remove the Drywall Without Crashing It on Your Head
Even with no nails holding the drywall in place stiction from old age may make it hard to remove. Use a larger pry bar to pull the bottom drywall away.
It should come out easily. If not check for nails you may have missed (there's always a few). Either stop and take out the nail or force the drywall hard enough that the nail rips through it.
Drywall is usually put in horizontally with a seam 4 feet from the floor. If that's how yours was done after you pull the bottom piece away the top piece can come out and fold along the seam to lay next to the bottom piece. Then they can be hauled away.
If your drywall was installed vertically you'll have an 8 foot beast to deal with. Wiggle it out and angle it. Get some help to haul it off.
Step 5: Then Just a Simple Clean Up
This is the only mess to clean up. So much easier than cleaning up all the debris and dust from demolition.
If done well the drywall should be in good enough shape that it can be reused with a little patching plaster to fill in where the nails were pulled.