I put this somewhere in the LGO forum, but its lost under a mass of posts so I'll repost it here.

If the lack of systematic grammatical detail in LGO leaves you confused, and trying to acquire the information peicemeal from the web leaves you frustrated, then I recommend you get a grammar book.

English speakers are fortunate in having available an excellent book on greek grammar written in english. This is "Greek - A Comphrensive Grammar of the Modern Language" by David Holton, Peter Mackridge and Irene Philippaki-Warburton (ISBN 0-415-10002-X).
It is very much a reference book, not a course book. I have used it, and can completely recommend it.
Here is a link that gives you some reviews and sample pages -

Comprehensive Greek Grammar

There is a shorter (and cheaper) book by the same authors entitled "Essential Grammar". I don't own this one so I can't personally recommend it.

Essential Greek Grammar

Of course there are other grammar books available - if other members have a favourite that they can recommend, perhaps they can add it to this thread.

Happy learning
Στιούαρτ