I'm always quite jealous when I read that someone is going to play it for the first time.
As mentioned a zillion times, easily my favourite series of games and I've finished DS1 countless times. But that first playthrough is amazing. I've still yet to find a game with such a uniquely bleak atmosphere, and once you start exploring and find how superbly interconnected the whole world is, it's just wonderful.
It's not a game that clicks with everyone, but if you get into it, you're in for a treat.
Hit me up if you need any tips mate.