Today Cold published an interesting post on his blog about The Only AH Add-On Required... Well, actually on the Cold's Gold Factory there are interesting posts every day, but I wanted to talk about this one in particular.
For Cold, the only add-on you will never need is your brain. Well, I quite disagree: there is another fundamental add-on you should use (especially if you're really using only your brain): Pen and Paper.
Writing notes is fundamental, even when you're using a lot of add-ons: since you're the one inserting manually your notes, the old fashioned pen and paper (or even better: pencil and paper) is nearly free of data-pollution risks.
Writing things down helps reasoning, and makes visualizing a lot easier. You have to choose what to write and what not to write (you can't just mindlessly collect data as Auctioneer would do), so every time you take your pencil you're making decisions. Having to make decision is good.
You learn more by applying and deciding than just by watching.
I remember that in my first days on the AH I used just my brain, pencil, paper, rubber and sometimes a calculator. This was years ago, at the beginning of the BC, and I used to strongly refuse to download any kind of AH add-on. Years later I finally decided to start using add-ons more and it certainly made the AH easier and faster... But I'm quite sure those years weren't useless (and, well, glyphs didn't exist back then, so I didn't have to post those huge amount of different little things).
(BTW, in Rift I'll have to go back to those methods, since there aren't add-ons O.o)