Where are the spark plugs located in a 1999 Toyota Camry?

The spark plugs in a 1999 Toyota Camry are located on top of the engine, under the plastic engine cover. To access them, you'll need to remove the engine cover. They're arranged in a V-shaped configuration following the cylinder arrangement of the engine. You'll find one spark plug for each of the four cylinders. A Haynes or Chilton repair manual for your specific Camry engine (there were a few variations in 1999) will provide precise diagrams showing their location.