They are the some of the same lessons that can be learned from Columbine, 9/11, Virginia Tech, and the Petit family murders, among many others. Here's what I have gleaned from current events.
1. You are alone and totally responsible for yourself.
2. The police are 20 minutes away.
3. When the police arrive, they are going to establish a perimeter, set up a command post, assess the situation, and work to ensure that they all go home at the end of the shift.
4. Having an active shooter randomly killing people does not change #3.
5. If you're on an airplane, they will scramble fighters to shoot the plane down. There is no rescue.
6. You should behave as if you were already dead.
It's time to start training. If the police are going to leave you in the nightclub to be shot when the Islamist gets to you, you have nothing to lose by fighting back. It would be ideal if everyone fought back, but that is unrealistic. Fight back anyway.
Select your moment, when his back is turned, when he is reloading, when he's text messaging his wife about how his jihad is going, and then go. Hopefully you have found something to hit him with, stab him with, a fire extinguisher to spray in his face, or perhaps you are armed with a firearm, whatever the rules are in your area. Use the tools and skills, but bring as much force and violence to the engagement as you can.
If he shoots you, well, you were already dead. Maybe the next guy gets him.
Even if I found a good hiding place, I am unwilling to be the guy who survived by hiding while a shooter executes women and shouts praises to his god.
It is reasonable to expect more attacks. It is reasonable to develop a personal plan. It is reasonable to talk to others and develop a group plan.
“If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun.” ― Dalai Lama XIV