Vacuum properly before anything wet
Most carpet dirt is dry grit, and a thorough vacuum removes it before any water turns it to mud. Go slowly, especially in traffic lanes, and pass each area twice in different directions so the brush lifts the pile and the suction pulls the soil out. This single step does more for how carpet looks than any shampoo.
Pre-treat stains and traffic lanes
Deal with spots before the overall clean. Blot fresh spills — do not rub — and pre-treat set stains and dark traffic lanes with a carpet spot cleaner suited to the stain, tested first on a hidden patch. Protein stains such as pet accidents and blood need cold water and an enzyme cleaner, never hot water, which sets them.
Clean in sections, and do not over-wet
Whether you rent a hot-water extractor or spray and work by hand, the rule is the same: use the least water that does the job. Over-wetting soaks the backing and the pad, which is slow to dry, can shrink or delaminate the carpet, and pushes old spills back to the surface as it dries. Work in overlapping sections and make a dry pass to pull as much water back out as you can.
Dry it fast
Drying is where a home clean is won or lost. Open windows, run fans and a dehumidifier, and keep the room warm with air moving across the carpet, aiming to have it dry within hours, not a day. Stay off it until it is dry. Carpet that dries slowly smells, can grow mildew in the pad, and wicks old stains back up from below.
When a professional is worth it
A home clean maintains carpet; it does not replace a deep one. For heavy soil, set-in stains, pet contamination that has reached the pad, or an annual reset, a truck-mounted hot-water extraction gets the carpet far cleaner and dries it faster than a rental can. In New York, carpet cleaning runs about $1 to $4 per square foot, or $50 to $150 a room.