Anytime you handle a firearm, always follow the basic rules of firearm safety. Keep the muzzle pointed in a safe direction, keep your finger away from the trigger, make sure it's unloaded, and put it on safe. Although the location of the safety can vary, never rely on a mechanical safety as a substitute for safe gun handling.
The most common safety location on a semi-automatic handgun is at the rear of the slide... but not always. Like on this World War II Japanese Nambu:
Sometimes the safety lever is also used to de-cock and block the hammer and disengage the trigger: and on some modern designs, there isn't a manual safety at all.
Young shooters should always have adult supervision and many adults often need expert advice about how to safely operate a firearm.
The magazine release can be located in different places, the most common is a push button. Although the release can also be found at the bottom of the grip.
On most semi-automatic pistols when the magazine is empty, the slide is locked back, but not always. Semi-automatic pistols usually have a lever that releases the slide,
and some are of unusual design.
Remember, firearm safety is your responsibility.
--Larry Potterfield