The thread is for discussion of a given episode, so it's assumed that if you're in here, you've seen it, and if you haven't, you should know better.
Perhaps; perhaps not.
I won't be seeing this season until the DVD comes out, and yet I read both these threads and some of the episode by episode reviews provided in the media.
First of all, my main interest remains with the books, from which the show has deviated significantly in many areas -- where I can tell, and has probably now done so in others, where I can't -- so there are no "real" spoilers for me. (Note that in the early seasons, there were far fewer deviations from the books -- books I had read -- and that did not spoil my enjoyment of the show at all.)
Perhaps I'll be more careful when it comes to next season, on the basis that the show will be showing GRRM's "bittersweet" ending -- bittersweet being GRRM's own spoiler -- but I very much doubt it.
A Song of Ice and Fire is, after all, more than just a (multi-)plot outline, as is
Game of Thrones. (And reading episode recaps is very much not the same as watching the episodes.) The show's highlights have included those much remarked upon one-on-one character interactions... some of which are not only absent from the books, but sometimes have involved characters that never met in those books. (Oh, and the Varys-Littlefinger dialogues -- all of them private -- were a real treat in the show. There is no way GRRM would have put them in the books, as he's clearly been keeping us away from those characters' thoughts.) Similarly, there are so many things in the books that have not made it to the screen.
Obviously, others may disagree, and if they are not sure, they should avoid these pages... and, eventually, news programmes around the time next season comes to an end....
As a wider justification of my own approach, I ought to say that neither hearing the 1981
Lord of the Rings radio serial, nor seeing the Peter Jackson films, spoilt the book for me when I eventually got round to reading it. Different media; different experiences.