Here's how to minimise soiling, and deal with spills...
1. Cover it up. If a period of heavy use or partying is looming, consider placing a throw over your upholstery as a short term protection. Any spills will be on the throw, which can be laundered as needed.
2. Vacuum regularly. Remove cushions if possible, and vacuum all areas including the back thoroughly with an upholstery tool, and a crevice tool for those tight corner areas. Gritty soil is EXTREMELY abrasive and wears fabrics fast. Vacuuming will keep gritty soils to a minimum.
3. Spot clean immediately. Any spills or dirty marks should be treated immediately with a safe, effective spotter (NOT the harmful foamy brands advertised everywhere today - these are not good for fabrics). Spots and marks left too long become more difficult to remove, and can become permanent over time. Always act fast.
4. Clean it. I'm sure you knew this was coming! But cleaning every 1 - 2 years will keep your upholstery looking its best. Professional cleaning using high quality upholstery cleaning solutions (NOT cheap and nasty generic chemicals), will remove gritty soils, oily soils and stubborn marks, keeping upholstery looking like new.
5. Protect it. A lot of upholstery comes with a fabric stain protector applied when new. This helps to repel spills and dirt, keeping fabrics looking good. This protector breaks down over time leaving fabrics open to damaging oils and soils. Replacing the stain protection is a very sensible decision. I regularly see it as the difference between fabrics cleaning like new, and permanent damage done that can't be undone. Renew your upholstery stain protection every 2 years and you won't go far wrong.