I think I am starting to grasp the idea of power spikes...but not fully.

So from what I can see...
Yasuo has a power spike when getting Statikk Shiv and then later when he gets IE
Rumble gets his when he gets a Haunting Guise and maybe scor shoes
Jayce gets one with a The Brutalizer
and so on...

Now those are power spikes with items...but with abilities I'm guessing it is quite different.

How do I know/tell when my champion is having a power spike and I start pushing my edge when I can?