If you're completely stuck on what to do in Fallout 3, CVG has you covered (SPOILER WARNING). They put together a short guide that will help you along on your journey through the game's main story missions and beyond.
Create a TON of new save files as you play, as it's very easy to have the game mess up your adventure, leaving you high and dry. DON'T rely on just the one save file!Sure, the guide is far from comprehensive and is filled with Spoilers, but if you're really struggling and don't want to purchase a guide or use any of the ones at GameFAQs, this is your guide. Be warned, the CVG guide gives a brief run down of every main quest and some of the side quests in the game.
To save yourself a lot of time hunting for Stimpaks, you can sleep in any un-owned bed for an hour to completely heal any crippled limbs and regenerate all of your health for free!