When it rains hard, I get a decent amount of water coming in through my chimney. Is this normal? What can I do to minimize this?
It's a relatively new house; it has a guard on top, and the chimney is in great shape.
Is there a chimney cap? If not, start there. If there is a chimney cap, and it's a brick chimney, odds are you have cracks and/or missing mortar--at which point I'd say your chimney is unsafe...both as a combustion exhaust (you don't want fumes leaking into the house) and as a safety issue (falling bricks hurt). I'd call out a licensed chimney inspector/cleaner/sweep.