Instructions
Complete "Mass Effect" on either the "Normal" or "Veteran" difficulty settings. This will unlock the "Hardcore" difficulty setting.
Choose "New Game +" from the main game menu. This will allow you to continue using your character from your previous play-through. Your character will retain his level, skills and equipment.
Change the game's difficulty setting to "Hardcore" in the game menu options. You must do this before completing the "Eden Prime" section of the game to still qualify for the achievements tied to "Hardcore" mode.
Change your teammates power usage option to "Limited" in the game option menu. This will allow you to more effectively use your teammates powers by giving you control over their usage.
Switch between characters and use powers constantly in battle. Make sure to use the appropriate powers on the appropriate enemy defense types. Tech powers tend to be effective against shields, whereas biotics are good against armor.
Stay in cover behind walls and barricades. Enemies deal increased damage on "Hardcore" and taking sustained fire will quickly kill you.
Keep your distance from enemies, particularly Krograns. If an enemy closes distance with you, backpedal while still firing on them.
Keep your teammates alive through the liberal use of "Medi-gel." In the lower difficulties, you can often get by with just your character alive. On "Hardcore," you will need the additional damage output that your teammates provide.