Make sure it's plugged in fully and check its breaker (push fully OFF, then ON). Kitchen and laundry outlets are often GFCIs — press RESET on the nearest one. Many 'dead' appliances are simply on a tripped GFCI.
Check the temperature dial hasn't been bumped, make sure vents inside aren't blocked by food, and pull the fridge out a few inches so the coils and rear fan can breathe. Give it a few hours to recover before judging.
An electric range needs its own breaker — check it. For a gas stove, if the burners light but the oven won't, or nothing lights and other gas appliances are out, it may be a gas-supply issue. Never leave a gas burner clicking without lighting.
Make sure the door is latched firmly (it won't start otherwise), the cycle is actually selected and started, and nothing is blocking the spray arms. Clean the filter basket at the bottom if drainage is poor.
The lid or door must be fully closed for it to start. If it won't drain, check for a kinked hose behind it. Don't overload it — an off-balance load can stop the spin.
If it hums but won't turn, it's jammed — turn it OFF, and use the small hex wrench in the underside slot to free the blades by hand. If it's totally dead, press the little red RESET button on the bottom of the unit.
You smell gas near the stove, see smoke or sparks from any appliance, or a burner keeps clicking without lighting — stop, unplug it if safe, and call us (911 or the gas company first for a gas smell).
Back in service — good. If an appliance keeps failing or won't come back, send a work order with the make and what it's doing so we can bring the right part.
Tell us which appliance, the brand if you can see it, and what it's doing (or not doing) — it saves a trip.