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Recently I picked up a black tarp that I put over a raised bed to cut down on weeds. Out slithered a little garter snake. I said, "Hi, cutie!" and let him go on his way.
Know where I learned that kind of composure? Right here, on DU. Someone posted a thread about prejudice against snakes (yeah, really) and I read it and said, "Ya' know, snakes aren't so bad." Actually, they eat a lot of pests.
So my little snake buddy is prob'ly still up there, feasting away on the bugs that are after my garden. 
I owe a lot to DU.
Cher
It is susceptible to a nasty pathogen or two that will live on in the soil if it gets established, and decrease your yields. When you first buy cloves to start your patch, be careful to peel them down to the bare cloves, and make sure you discard any cloves that look like they've been disfigured or 'eaten'. When I got mine from territorial seeds a half decade or so back, I discarded about a third of what they sent me.
Then I soaked the cloves in an alcoholic solution over night. (Mouthwash, actually 
This let me peel off the finest layer of the skin to make sure nothing else was hiding in there, and hopefully killed off any bugs hanging around from the rest of the head that I'd discarded. Then I rinsed them off and was ready to plant.
You shouldn't need to do all of that each year; you just want to make sure you're not inoculating your soil with any nasty pathogens that hitched a ride on whatever the commercial grower might have sent you, to ensure the best crops going forward.
Then, each summer when the green shoots have yellowed off and dried and it's time to harvest, I hold back the biggest and best heads to use to replant in a couple of months when the soil cools down. I usually end up harvesting in maybe July and planting in October or November where I am.
As far as replanting, I'm not sure what other folks do, but I always carefully peel the papery skin off the cloves before replanting them. I don't know if other folks bother to do that or not. But between planting and harvesting, I basically ignore them. If I go too long without rain, I'll water them, but it's infrequent that I have to do so.
Winter - if your winter gets extremely cold, it'll kill them. We had a week or two of lower than -5 F or so weather a couple of winters back, and it killed about half of my crop. So last year I put straw over the bed as an insulator, but the winter turned out fairly mild after all, so it wasn't really needed.
