I am currently playing through Hardcore mode, and it is not as hard as you think. The difficulty is exactly the same as Zealot, just you only have 3 saves.
A good thing to do is run a parallel save file on easy, to practice the areas that are coming up on the hardcore playthrough. Also, Use the plasma cutter (best weapon in my opinion) and the Pulse rifle (to make really easy work of the pack and other fast moving necromorphs (I chose this because it has a fast rate of continuous fire so it makes things easier on me)).
My play is to save on chapters 5, 10 and 13/14. 5 because it is about a third through the game, 10 because this is when things start to get harder, and 13/14 because the end of the game will be really challenging on Hardcore mode, so you won't have to go far back if you die. The saves are also evenly spaced out as well, so you will never have to replay more than 5 chapters if you die.
Also, if you are on the Xbox 360, because there is 2 discs, when you put in Disc 2 on chapter 7 I have heard that you get one checkpoint because of this (checkpoints are also disabled on Hardcore). This is (kinda) a bit of an exploit I guess, but unavoidable because of the two discs.
Just take it slowly and carefully, be conservative with your ammo, and be prepared. You will know a lot more about the game than you think because you have already played through it once, it gets a lot easier the second time you play though it.
Good Luck with your Hardcore playthough
