The strategy I follow is this:
Site templates: try to feature it so it comes out in the morning (8-9am EST) or early afternoon (2-3pm EST). They take about an hour to feature. It's best to submit them just before the hour (:55 or :56) to get a good position in Latest.
Original templates: who knows?
It seems like there's a huge batch of templates released some days at around 2pm, including original templates. I've seen a 2 or 3pm release with up to 20 pages of new memes.
So, I guess in theory if you were submitting an original template, a good time would be far enough before that deadline to give the mod time to approve it, but not so far back that it's buried deep in those 20 pages.
But take that with a grain of salt, because it's anyone's guess with original templates. Sometimes you get lucky, sometimes you don't! :)
Caption this Meme
