Due to living at home, part of the agreement worked out with my family is that everything I bring home must fit in my room. So, I can't quarantine new animals anywhere except in the same room everything else is in.
So, with that in mind, I don't purchase breeding age animals close to breeding season (less temptation), I try to purchase from either someone I trust (like the pastel from BHB) or from a place where I've been able to observe the animal for a few weeks (such as the petstore I work for).
When I bring it home, it's housed in its own tub, usually on a shelf separate from the main group of snakes. I wash my hands inbetween handling it and handling the others. I also spray the tub and surrounding area once a week with lice spray for about 2 months (I also do this to the whole collection if anything at the store I work for comes down with mites). I keep an eye on the snake, and once it's eating regularly, defecating normally, and behaving normally at the end of the two month period...it just stays separate because there's no reason to mix the snakes if it's not breeding season anyway. 
The result has been that the shortest quarantine any of my snakes has had was about 5 months, when I got my first male.
This method works for me and my small collection - not a single mite outbreak, URI, or any other sort of disease or parasite has reared its ugly head, knock on wood.
Breeding - I've just got the one breeding age female, so my biggest concern is making sure both animals have enough time to themselves. I found with last year's male that leaving him in until copulation, then taking him out for a two week break (more for her sake than his), seemed to work. This year she seemed to get knocked up after one accidental breeding a few months ago, and the intentional one a few weeks before ovulation.
I hope you get more responses!
~jenny
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"Polysyllabism in no way insures that what you're saying is actually worth being heard." - Blake (an e-friend of mine)
"I have never made but one prayer to god, a very short one: "O lord, make my enemies ridiculous." And he granted it." - Voltaire