I stir just a little so it doesn't boil over, but I'm boiling all the wort. If you're boiling a smaller amount, you want to stir enough so that it doesn't scorch on the bottom. No need to stir constantly, though.
You should have your wort at a boil the whole time. You start your timer when you add your first hops, and boil for 60 minutes. A boil is actually a rolling boil, not just hot, or a simmer.
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