I'm currently in the process of doing hardcore myself (I've gotten to chapter 9 where I made my second save). I've died once in chapter 2 in the laundry room because I panicked, and I nearly got killed by the last pregnant in chapter 8 as it ripped itself open while I wasn't paying attention (swarmers dropped my health to the last bar!). The very best advice I can give is to watch walkthrough videos on YouTube, preferably several of them so that you can see different tactics to each area and choose your own.
Here are some YouTube videos of the beginning of some playthroughs that I found very
Also, there are several other videos available for each chapter on hardcore if you simply search for it (f.e. dead space 2 chapter 7 hardcore).
If you can spare the extra dime, get a DLC for the suits and the weapons, as it does come in handy. Although I did buy the Martial Law pack a while ago as I thought it was the achievement DLC, I rarely ever used any of the DLC weapons. I went with the PC for the most part, but I had a Force Gun in my inventory for safety, but it wasn't really
needed. I did the Detonator glitch right after the disc switch because I knew the tripod elevator was coming up and I couldn't afford ammo for it. Glitching for cash is pointless, it takes AGES and you'll just be bored out of your mind.
Do not freak out during the events where you have to shoot glowing points or canisters or else you die, you have more time than you think so you can really take it easy (although not too easy!) The church grab and the tormentor was a couple of my most feared events, but I didn't have much problem with them at all.
Take it slow, watch videos so you know where to anticipate enemies and make sure you have enough health and ammo (I always keep 4 health packs and 50 PC ammo).
But as I said, learn from videos! I breezed through several areas because of that. I'm going to try to make a run for chapter 13 up to the eye poking machine. I'm not even nervous about it like I was before starting my HC run because now I know it's not really THAT bad, as long as I stay focused!