If you are more than 100 feet away and the lion hasn’t notice you, leave the area and report your sighting. Hiking, preferably in a group, make noise. You do not want to surprise a lion.
Most mountain lions will try to avoid confrontation. However, if you are spotted, appear confident and ready to defend yourself. Do not turn your back. Growl and show your teeth. Never crouch. Stand tall, put your arms up and/or hold your shirt or jacket open to appear larger. Grab any weapon, branch or rock, and wave and shout at the lion. Keep your eyes on the lion and try to stare him down. Be aggressive. You want to scare it away. If close enough, throw things at the lion. If you have a gun, use it.
Do not try to run. You must back away slowly.
Be aware that smaller children are more vulnerable.