An old-fashioned method, but a good one. Shaking down your rug is a fantastic way to remove any surface dirt and dust. Take your rug outside, and give it a good shake to loosen any dust or crumbs that might be caught.
If your shag rug is too big or heavy to shake down, try beating it. Hang the rug over something solid, and beat it with a broom. This should knock any debris loose.
Once you've given your rug a thorough shake, leave it to hang outside in the sunlight for a few hours. The exposure to sunlight can help to kill any germs that are trapped in the pile.
It is possible to vacuum a shag rug, but it isn't as simple as vacuuming a carpet. A vacuum can pull at the fibers and pile of the shag rug and cause it to shed.
Instead, check to see if your vacuum has a high pile head. This is softer on the shag rug and doesn't have the same whirling motion that can pull at the fibers. Thoroughly clean the shag rug using the high pile setting.
If you don't have a high pile vacuum attachment, there is still a way to vacuum your shag rug. Flip the rug upside down, and vacuum the underside of the rug. Then, remove the rug, and vacuum the space where it was.
If anything gets spilled on your shag rug, try and clean it before the stain sets. Because of the high pile, there are more fibers for the stain to stick to.
Begin by blotting the spill. Use a dry towel cloth to absorb as much liquid as possible or a damp cloth to dilute the stain. You should dab, rather than wipe, in order to keep the spillage localized.
Mix a few drops of dish soap with hot water. Use a brush with soft bristles to scrub the area carefully. Rub the stain until it's gone. Rinse through with water to remove the rest of the soap solution, and leave to air dry.
Begin by blotting the spill. Use a dry towel cloth to absorb as much liquid as possible or a damp cloth to dilute the stain. You should dab, rather than wipe, in order to keep the spillage localized.
For set stains, use a carpet cleaner, and spray it directly on the stain. Leave to sit for a few minutes, before wiping away. For a homemade solution, mix warm water and white vinegar in equal measure.
Although you can't just run a vacuum over it, cleaning a shag rug doesn't have to be complicated. Just remember to shake it out on occasion, and treat any spills as they occur. That will keep your shag rug soft and plush for longer.