Start by cutting a strip 4cm wide and 1m long in one corner of the carpet.
Use a flat head screwdriver and a wrecking bar to gently pry the strip off the tacks underneath.
When you can reach in under the carpet, pull up the whole corner. Then follow the edge around, pulling the carpet up and rolling it into the centre of the room.
Once the carpet is all up, get a couple of people to help you take it out.
Once the carpet is out of the way, pull up the underlay. It's really the same process as removing the carpet, although it should be easier to start.
Pull up from the edges and roll it all into the middle of the room. Once again, you'll need help from a couple of people to carry it out.
Then use a pair of pliers to pull out the staples that hold the underlay on to the floor.