for me it depends on the deck. if it's in the deck i'll use it, if it's not i won't force it. there are many/most decks i read with no thought about that aspect of things at all.
when i do, it's only in the way lrichard described, basically, as that is pretty much the limit of my astrological knowledge anyway, lol.
for me it makes sense. i have something of an interest in sun signs and have for years. whenever i meet someone i ask them what their sign is if i can work it into the conversation. sometimes in class i will doodle...sometimes its numbers in arabic, sometimes its abstract designs, and sometimes its astrology symbols for zodiac and planets because they are pretty. so there's that.
it makes perfect sense that in this, as in other aspects of tarot, background would inform reading style. if you have no interest in anything astrology related, makes sense that trying to bring it into reading wouldn't do it for you, and no reason to force it, the way i see things. if its one of those things floating around in your head anyway, i don't see why not connect them sometimes, if the deck is right.
but then, i kind of have a thing of synthesizing tarot with other aspects of my life/interests. thus my use of memory exercises, connecting tarot reading to self-help book exercises, using draw to ponder things i am reading about like ethnic war or whatever, do draws about structure and content of papers i am writing...i like experimental synthesis of that sort.
different strokes for different folks. my 'astrology' is elemental dignities. they do nothing for me/cannot connect/make that concept make sense to me in the least :]