To be a super good fallout player, follow these steps and you can become a pro. Fallout is my favorite videogame EVER.
1) CONSERVE YOUR AMMUNITION. In the begninning, i usually stick to melee weapons because they're effective and good to use when you're saving up your ammo. NOTE: Some melee weapons can and WILL become super bad, but hopefully by then you have a surplus ammount of ammo.
2) ALWAYS REPAIR ALL OF YOU GEAR. Running around with low-condition gear either armor or weapons won't get you very far in the game. I learned to always repair and keep track of your gear. If you don't, game over.
3) LOOT EVERYTHING EVERYWHERE. Even if you don't need the loot, it's always good to maybe go and sell it somewhere or even sometimes they can repair a super good weapon of yours. Be sure to check every corner of every building of every location in the game!
4) TRY TO HAVE A COMPANION. I played fallout new vegas before fallout 3 and I learned that companions are VERY usefull. Why? Because they can help you CARRY your equipment of maybe they cant take heat from the enemy while you think of a strategy to kill the enemy. In fallout 3, your companions die, in fallout new vegas, they don't. The only companion i know that is strong in fallout 3 is Fawkes and he is just awesome. But from some comments I looked at said that he can die from car explosions. So some advice, maybe stay away from cars. He doesn't go unconcious, but he can take your kills and take your exp away from you.
5) SIDE WITH THE BROTHERHOOD. First of all, why not? They're the good guys and the enclave are the bad guys. The brotherhood have a lot of gear for you, aid, ammo, and other stuff. So just be nice to them.
6) TRY TO HOARD. Ok, this one you guys might be thinking,"Why? This guy is crazy why would I hoard useless items i might not need." This is sort of true. You don't need to hoard useless items, but sometimes just those few couple items you just 'happened' to keep might just save your life. There are a lot of weird and random encounters in the wasteland. Always be prepared and cautious of all times or you might just ♥♥♥♥ your pants.
7) GET RARE WEAPONS. There are plenty of guides to rare weapons on youtube, in fact, i might even make guides on here to get them. But the rare weapons are just better versions of the previous one. They're better in all of the stats of the original weapon but they don't look unique.

That is my guide for you to go off to a good start on Fallout 3. If you have any questions, just ask! I'm open to anything you ask because after all, fallout is my favorite game. Hopefully this has helped you, even if it was just a little bit. Also give me input on the guide, was it good, bad, O.K., tell me because that was my first guide and i want to know how i did. Thanks for reading!