Say you want to make a nice doorway with 2 doors. A pressure plate will only open one door at a time, and manually clicking 2 doors to enter your house can be annoying. There's a simple fix to this problem using redstone. With a little redstone wire and a redstone torch, you can make it so that one pressure plate opens 2 doors at once. This method works with both wooden and iron doors and stone or wood pressure plates.
First, set up your double doors. Make sure that both doors are hinged on the outside blocks instead of the edge of the other door.
Place a pressure plate on both sides of one of the doors.
Dig a hole underneath the doorway.
Place a redstone wire on the block below the pressure plate.
Place a redstone torch on the side of the block next to the wire. Technically the torch will be filling the block below the door that has no pressure plate.
Put another redstone wire underneath the other pressure plate.
Fill the hole up and both doors will open from one pressure plate.