Kosma,
My main reference is orthodoxinfo.com, but I also spread out my searches to other sites and asking people. As for sharing pearls with swine, I think discussing why Orthodox and papists are different, helps them see the tradition that they abandoned. I wouldn't discuss the Holy Mysteries with a non-Orthodox. Although many Orthodox, by name, aren't ready for the knowledge either. That is knowledge beyond their understanding and would do more spiritual harm. Of course, I take into consideration, the person's disposition. For example, a papist may want more spiritual info and not want to hear about the ecclestiastical aspect, yet. And I can always point out something spiritual which will reveal the Orthodox truth, like this example of crossing ourselves. But, I leave it to God, to reveal what the person needs to hear by letting the person ask the question first. You can't know what would turn them around. For me, it was learning about the Great Schism. When I learnt about that, Orthodoxy became crystal clear.
In this case, I wasn't asked yet, but the question came to mind and I figured I should do my homework and have the answer, in case the question comes up.
I guess I'm looking for why do you do this or why do you have that, type of answers. Don't get me wrong, I'm not honing myself to proselytize. This is for my spiritual insight too.
In Christ, Joanna