It is a book about general usability testing.
Some common sense you should follow and notice.
Other things are:
1. Every design you need to say a reason why you design like this.
2. Every user no matter the user or the develpor,manager,marketing colleagues etc. you need to get to know why they say this and thus you can find a solution to fit in with in design.
3. Learn the priority and cost. Make balance ,what is important? What is less important? How much effort you need to make this adjustment.
Things are always change, do more ,see more and think more!