The biggest mistake people make is not watering enough- the garlic comes out really small with insufficient water. We keep the sprinkler going on the garlic bed for 8-12 hours after planting. (It's an oscillating sprinkler that goes back and forth over a large area. For a smaller area, maybe 2-4 hours would be sufficient.) This soaks the ground deeply and protects it through an average winter until February, when we water again. During an extra-dry, windy winter we do an extra watering in early January or so.
When Spring comes, treat garlic like your other garden vegetables, watering as much as lettuce or tomatoes.