What is the FIRST and most important rule of shop safety?

Shop safety is paramount — most shop injuries are preventable. Core safety principles: EYE PROTECTION at all times (safety glasses or goggles; full face shield for grinding or splash hazards); standard sight cannot be replaced if damaged; even momentary eye protection failure can permanently injure (lawnmower blade hits a rock could send a projectile into eye; angle grinder disk shatters into high-speed shrapnel; saw kicks back chip as flying debris). HEARING PROTECTION (table saws, routers, planers, vacuum cleaners exceed 90 dB; prolonged exposure causes permanent hearing loss; foam plugs or earmuffs or both for very loud). RESPIRATORY PROTECTION (dust masks N95 minimum for general dust; respirators for chemicals, treated lumber, MDF/particle board with formaldehyde, spray paint, lacquer; silica dust from cutting masonry, concrete, certain woods causes silicosis). APPROPRIATE CLOTHING (close-fitting; no loose sleeves, dangling cords, ties, jewelry, long hair tied back; they can get caught in spinning parts; sturdy closed-toe shoes). GLOVES for handling rough materials, sharp edges, chemicals; but NEVER WEAR GLOVES with spinning tools (drill press, lathe, table saw, router) because gloves can catch and pull hand into the tool. Hair control: long hair tied back. WORKING SAFELY: read instruction MANUAL for any new tool before use; understand controls, capabilities, limits; NEVER REMOVE safety guards or defeat safety features because they exist due to past injuries; ONE TASK AT A TIME (don't multitask with power tools; full attention required); UNDISTRACTED workspace (clean area, proper lighting, no obstructions); children and pets out of shop; NEVER OPERATE while impaired (alcohol, drugs including some prescriptions, severe fatigue, illness); BE PREPARED for emergencies (first aid kit accessible, fire extinguisher of ABC type, phone for 911, know where breakers are). ELECTRICAL SAFETY: GFCI outlets in shops and outdoors; check cords for damage; don't use power tools in wet conditions; UNPLUG when changing blades, bits, accessories; don't overload circuits; use heavy-duty extension cords; grounded tools (3-prong) for safety unless double-insulated. FIRE SAFETY: combustible materials away from heat sources; saw dust accumulates and should be cleaned regularly; SOLVENT-SOAKED RAGS can spontaneously combust so store in metal containers; welding/grinding sparks fly far so clear area and have fire watch; spray painting and finishing produce flammable vapors needing good ventilation. CHEMICAL SAFETY: read SDS (Safety Data Sheets); ventilation for fumes; skin protection for solvents and adhesives; eye protection from splashes. ERGONOMICS: lift with legs not back; don't lift more than safe; stretch and rest during long sessions. KNOW HOW TO STOP each tool quickly (foot pedal release, panic button, etc.); know first aid for cuts (direct pressure, elevation, call 911 for severe); have current tetanus shot.