The principle. Edward Hall's proxemics research mapped four distance zones: intimate (<1.5 ft), personal (1.5–4 ft), social (4–12 ft), public (>12 ft). Sales lives in personal and the inner edge of social — roughly 3–5 feet for most Western contexts.
Door knock. Knock, then immediately step back to ~4 feet. They open the door without feeling crowded. That single step changes their first impression.
Kitchen table. Sit at the corner, ~3 feet apart. Close enough to share documents, far enough that they don't feel cornered.
Demo room / showroom. Walk the customer through, but never directly behind them — that's predator positioning. Stay at their elbow, slightly off-shoulder.
Cultural calibration. Latin America, Southern Europe, Middle East: tighter zones (~2–3 ft is normal). East Asia, Northern Europe: looser zones (~4–5 ft minimum). When in doubt, mirror their distance.
Watch out for. Closing the gap too fast on a first meeting reads as aggressive even if your words are warm. Earn proximity by minute 5, don't grab it at minute 1.