The Eight Gates are a frequent topic that comes up in taijiquan.  There are many takes one what each one means.  For example, there areseveral points of view on what exactly push is and what part of the body you use to execute it.  As you can imagine, there are many conflicting ideas and some that agree. 

It's always helpful to read over these when you run across them and weight them about against what you know of the gates being discussed.  Sometimes it gives you a window into a posture or technique that you hadn't thought about. At the very least, it gives you a framework to mentally work through your forms and consider what is going on.

This article considers the eight gates from a technique point of view as well as a general principle.  While push hands players might have a bit more hands on experience with some of the instances that he talks about, it's a good discussion for us all, as we are all involved with that imaginary partner on an intimate level when we're doing solo form. 

Take a second to think about each gate in your form and share what you take from his point of view.

You can find the full article by clicking here.
http://slantedflying.com/the-eight-gates-techniques-or-principles/