Hi there!
There are some helpful articles to (at least) guide you when it comes to reviewing, and I've linked them below:

"Invalid Item" 
"Guidelines To Great Reviewing" 
"Sisco's General Advice For Reviewing." 

The bottom line is that everyone has their own method of doing things. So there is no 'set rule' for how an individual's reviewing style should be. Just remember to keep the basic principles in mind "Respect-Honesty-Encouragement" in mind and you should be fine.

Or as they always say "put yourself in the writer's shoes". What kind of a review would you like to see showing up in your inbox? Have that in mind when giving your feedback as well.