Markos, thanks for mentioning my blog -- I started it from purely selfish motives, but I would love for it to be helpful to others as well. As you said, anyone's welcome to comment -- in fact that would make it more useful for me and for others too.
For the OP, what revolutionized my own study of Greek was attending Christophe Rico's Polis course in Rome last summer (http://www.polisjerusalem.org/?page_id=6
) -- four hours a day for four weeks of comprehensible input in Koine Greek. When I left, my reading speed had nearly doubled, and what was even more important, Greek had become a living language
to me, just like my Spanish and French. I no longer had a running translation in my head when I read Greek, and I could even begin to produce it without spending minutes searching for the right form of each word.
So the keys for me were:
1. Comprehensible input and lots of it. John, Mark, Matthew, Luke, and Acts are usually good authentic sources of comprehensible input, depending on one's level. But aural input is really important too. Unfortunately it's much harder to come by.
2. Production. Write and speak Greek as much as you can. It doesn't matter how basic your utterances are. Just do it. Begin with very simple sentences -- ἄσχολος εἰμι. ἔρχομαι πρὸς τὸν φίλον μου -- and gradually increase complexity. Try to do it as spontaneously as possible. I find that comprehensible input is more valuable to me after trying to speak and write has made me aware of the gaps in my knowledge.
Rico has a book, Polis, which you might find helpful. It's available in French, Italian, and German, and he's working on an English translation. But most of the text is in Greek anyway, so it doesn't matter that much.