Good points!
I just wanted to improvise a couple of points that you mentioned.
What to avoid in reading : ........................................... thread after first 3 pages.
Actually, someone should never see the quantity of the pages a thread has got and consider it to be a spam thread. Some useful discussions take way more than that so they might cross that limit. Or threads like the announcements, where theymos announces something and others start discussing it in there, are threads never to be avoided, specially by new users. So a person should only avoid reading a thread which starts with a spammy and useless question and is carried on in that manner for the first two or three pages.
While replying, do not quote the full post of OP, specially if OP post is big.
A quote should only contain the part of the text that you are replying to. So no matter how big or small it is, you need to cut out the parts which has no relation to what you are writing. Even if the opening post is in two sentences, you need to quote only one of those sentence if you are not talking about the second sentence too. Even if you want to talk about the second sentence as well, make a separate quote for it and write the content related to that in there for more clarity. That would make your post look more clear, and people would enjoy reading it (as long as it has some logic).