What Attributes in an item that makes its gg / good to sell?
Ex 70% EE?

depends on the item and its tier.

if you find an item your not sure about, put its mods into the MP and search for items similar to it to get an idea.

http://forums.d2jsp.org/index.php?showtopic=18427600&f=272 - this is helpful if you havent read it yet

You can almost always assume that if it has lots of enhanced effect then it is good. The only exceptions I can think of are robes and medium armours

But other desired mods are high strength, dexterity, intelligence, magic luck, extra item slots, and life steal (though not nearly as much as it used to be). There are a couple more too, but those are the main ones - especially strength, dexterity and intelligence