Well, I’m just curious because, well, I get depressed at times that I’m practicing sight reading and it’s just like brainfart, brainfart brainfart. You know? It’s like "Hey! I knew that was B! But why didn’t I recognize it at an instant?" I am a very good piano player, but I refuse to live my life playing by ear. I can read sheets, but slowly. I have been practicing two hours a day for the past two weeks(sigth reading) and it just seems like stuff still isn’t getting clearer. And by two hours, I mean once in the morning and once in the evening. I am practicing on simple sheets. VERY simple. And even a metranome at half of the tempo. I know that it takes time, A LOT OF TIME, but I would just like to hear other’s opinion’s on how I should practice and what kind of sheet(specific sheet maybe). Please don’t suggest any books. Oh and how long did it take you guys responding to my insanely long question to begin to GRASP sight reading. By grasp, I mean like simple songs are just a lil’ to easy for you.
My esteemed colleague Jack has put his finger on it *precisely*: it means that you render the piece on sight at full performance speed, with all its dynamic & agogic inflections etc in place, ‘as though you had been working on it and reached a considered view for performance’.
In order to learn to do this, you have to take yourself back *down* the repertoire ‘ladder’ until you hit a level of difficulty where you can achieve all those demands. If that means going back to ‘My first piano book’, don’t worry about that and don’t let pride get in your way.
The key to the whole undertaking is that you learn to process musical information — *ALL* the musical information — in a split second, without this interfering with any other of your tasks, musical/mechanical, that you have to perform at the same time.
By taking yourself back, if needs be to ‘rock bottom’, you establish a level at which you can answer all these criteria. You then, over time, up the ante as regards complexity *gradually*, never allowing yourself to ‘let yourself off the hook’ by relaxing speed or expression demands *ever*.
Do that, and the ‘knack’ will come to you very quickly, comparativelyy speaking, compared with "sight reading" slowly, in which case you will *never* achieve that skill *at performance speeds*. The latter, actual performance speed, is the one criterion which is non-negotiable.
As regards the practice method, as you can only sight read *ONCE* <g>, Bach chorales (and anyone else’s chorales) are a very grateful resource as there are thousands of them, so you won’t quickly run out of cannon fodder. 
Good luck, hang in there, and all the best,