Altitude sickness

I’ve been reading up on how to avoid getting altitude sickness while visiting Colorado. As you all know I’m going there in just over 3 months time.
I want to avoid it! I do not want to get it if I can help it!
Has any of my readers ever gotten altitude sickness? If so how do you avoid it? What tips do you have for me?
I’m all ears!
I seriously am hoping I wont get sick on my trip! I will just drink plenty of water!
Even if you’ve never been to Colorado, have you been somewhere where there is or was high altitude, and if you have, what did you do to avoid becoming ill?