Where's your breaker box? Or maybe you call it your "fuse box" (old school), or "load center" (if you're an engineer or contractor).
This is something you need to know, even if you live in New York fucking City and have a Super to take care of this.
It's not enough just to go to the box and find the breaker and reset it. You really should know what else is on the circuit, because it may have been something else that tripped the breaker.
What do we do? We label the breaker box, and then we label each outlet and connection!
Why do we do it? Because the power loss that you notice might not be the cause!
For each power connection you should know from either end. By this I mean that from the box you should be able to know what is on the circuit, and from the connection you should know the breaker.
How do we do it? I'm gonna tell you how.
There's the easy way. This way takes two people, one at the box and one wandering around with a big radio and a cell phone. Plug in the radio, and have the guy at the box trip breakers until the radio goes off. Make notes accordingly. Repeat until all the data is collected, and then compile. Make sure that you duplicate efforts in kitchen and baths with GFCI (Ground Fault Circuit Interrupt) outlets, to find which are on the GFCI. I've found bathroom GFCIs feeding outdoor outlets as well, so be persistent.
The hard way is exactly the same, but turn the radio up to eleven, and trudge back and forth moving the damn thing, making notes and then compiling.
Here's the great part, the part that makes your OCD subsystem happy. The compilation. Breaker one-nine breaker one-nine. Sorry about that. Each breaker has a number, and handles a certain number of outlets. Label each outlet with the breaker number, and a number of its own.
Now you can tell if a particular circuit is being overloaded because all of your daughters are using their blow dryers at the same time, or if it's because some weasel has put the fountain pump on the same circuit.
ProTip: Label each outlet on the inside of the cover with the breaker number. Leave a copy of the breaker index (1: kitchen counter outlets, 2: kitchen baseboard, etc). Take all that info, put it on a schematic, laminate the puppy, and keep it inside the breaker box.