There are a LOT of things that we rate on. Here's a description of what we rate and how we look at things.
Scores:

Cleanliness
This should be pretty obvious. There should not be a lot of paper on the floor, trash everywhere, and general cleanliness. I'm not saying that I have to feel like I could eat off of the floor, but it just should not be full of litter.

Smell
Does it smell like a dead body? Is there an overpowering scent of air freshener? If you said yes to either question then it gets a low score. My sense of smell isn't the best so if I can tell it's bad, it's bad!

Lighting
I like to see where I'm going but really harsh lighting bugs me. I'm looking for a happy medium here.

Soap
I check the smell, how soft it leaves my hands, and if there is any of course. I'm a fan of bar soap but some may enjoy the liquid kind.

Mirror
First, there should be a mirror. Second, I should be able to look in to it ans see that's me!

Fixtures
Ever go in to a restroom and find out that something doesn't work? Doesn't that piss you off? Well, it does piss me off. Everything that's available to the user should be in working order. I want the door to latch, I want the water to run, and the paper towel dispenser should give me paper towels!

Lighting
TP Ply matters and so does transparency. If I can see through the one measly ply of TP that's there, it's crap!

Water
Three things on this one. There should be access to water, it should get hot fast, and the water pressure should be decent.

Hand Drying
I hate air dryers. They're loud, take forever, and don't get my hands dry. There is some bias on my hand drying scored because of this. I mainly look at if it's available, the type, and how well it works.