Blot the wine up with a dry cloth, pour a thick layer of salt over what is left while it is still wet, leave it for several hours, then vacuum when it is bone dry.
- Blot, do not rub. Press a dry white cloth or kitchen paper straight down and lift it away. Rubbing drives the pigment deeper into the pile and pushes the edge outwards.
- Work from the outside in. Start at the edge of the spill and move towards the middle, or you will finish with a mark larger than the one you started with.
- Pour salt on while it is still wet. A thick layer, covering the whole mark. It will turn pink as it draws the wine out.
- Leave it alone for several hours, or overnight. This is the step people skip, and it is the step that does the work.
- Vacuum when it is completely dry, then treat anything left with cold water and a drop of washing-up liquid.
Hot water is what ruins this one. Red wine is a tannin stain and heat sets tannin into the fibre permanently, which is why a spill that has been attacked with a hot cloth turns brown and stays brown. The same applies to clothing: never put it in a tumble dryer until you are certain the mark has gone.
Salt is hygroscopic, meaning it pulls water towards itself. While the spill is still wet the salt draws the liquid up out of the pile and the pigment travels with it. Once the wine has dried there is no water left to move, which is why the whole tip depends on doing it straight away.
Household chemicals can be dangerous in combination. Never mix them, keep the room ventilated, and test anything on a hidden patch first. Full disclaimer.