Play the game from start to finish in Hardcore Mode.
Hardcore Mode is new to Fallout, and adds more realism to the game. While playing on Hardcore, all ammo has weight, your stats include H2O, FOD, and SLP. If any of these stats reaches 1000, you will die. You must keep yourself properly nourished by eating, sleeping and drinking. Also, Stimpaks heal your health over time rather than instantly. and they will not be able to heal your limbs if they happen to break. Companions CAN die while in your party, and CAN be hit by friendly fire. Although Hardcore adds more realism, you CAN set the difficulty to Very Easy to make the game easier on you.
To achieve this, you'll be prompted to turn Hardcore mode on before leaving Doc Mitchell's house. You must choose yes to get this achievement After turning it on, you cannot turn it off for the rest of the game. This means you must get to the end of the Battle for Hoover Dam without ever having turned it off. The achievement should pop just as the ending cinematic starts.
- You'll want to have some reasonable level of strength, as weapon ammunition has weight (especially energy and explosive ammo) which will make a large dent in your carrying capacity.
- Always have at least three doctor's bags on you at all times as your limbs will most likely become crippled. Don't take the Small Frame trait!
- Keep in mind easy access to water and food sources. Two rad-free water sources that can be conveniently accessed are the well in Freeside and the sink in the Presidential Suite of Lucky 38. The Gourmand in the Ultra Luxe also usually has a large supply of food for sale.
- If an item has a + in the Hunger, Thirst or Sleep stat, this is bad! You want negatives (-) so you can reduce them down. With this is mind, note that alcoholic beverages and Nuka Cola actually make you more thirsty.
- Enemies have significantly more health, so if it gets too challenging turn down the difficulty before turning off hardcore mode.
A special thanks to DarthRandalNC, who wrote an extremely detailed Hardcore mode guide here.