Minor disagreements are inevitable. Here is one now! :
-)
"Read before write" is something I would direct more at those answering questions, but you are of course right that it is important to do so on the other side as well. And to me it is a bit clearer leaving out "poster"/"responder" from the headings - we are all posters to the forum, right? But the intended meaning is still obvious of course, so no big deal.
Another common issue might be worth including, that of asking a question in a way that is too specific. I see it all the time, it even has a name, which I of course can't remember. (something like "X not Y")
What I would like to suggest for inclusion is something like this:
For those seeking advice
Always make it clear what it is that you are trying to accomplish. Stating a problem very narrowly makes it harder to take a big picture view and come up with good solutions. "I need to travel to Germany" will yield different (and better) answers than "I have a bicycle. How do I make it go really fast?".
For those offering assistance
Make sure that the question you are responding to is the one that is being asked. Sometimes we jump to conclusions and what is in our heads is not the same as what is in front of us - getting it right the first time saves time and effort on your part and avoids confusion.
Perhaps those two sections should be under a common heading of "how to ask and answer questions" or someting similar. Right now it might give the impression that this place is only intended for technical questions and answers.
Just to be clear, what's already there is good, and I'm glad you took the time to write it down.