I usually find starting new role-playing games more of a chore than fun. I prefer to just dive into games, but in this genre it's advisable to learn how various elements work or you could miss something important. I never look forward to this part as I tend to obsess about what's the best way to spend skill points and agonize over choosing the "right" talents, which translates into lots of reading other people's opinions. I felt the same way in the beginning of Oblivion, but ultimately ended up loving that game, which made the hours of research worth the effort. Of course, not everyone obsesses the way I do, so it's a case of "know thyself".
The first level of a game usually acts as a tutorial, but I didn't quite see the necessity for such a long lead up in this game starting from babyhood and taking you through some consequential pre-adult birthdays. Although there are some story details in here, it could have been done in less time. But RPG's are typically very long, so be prepared to spend a goodly number of hours here.
The story revolves around a nuclear holocaust that turned the world into a total wasteland. Some people survived the devastation by escaping into various vaults and staying there throughout several generations before emerging into a barren world. Having been raised by his father in Vault 101, our hero is a young man who is completely ignorant of the outside wastes. However, when his father suddenly leaves the Vault without warning, he decides to follow his trail. In his quest, he becomes educated to all the dangers of the area known as the Capital Wasteland and meets people who will give him side missions. All of the water is irradiated and finding a solution to this is the theme of the main quest.
In the beginning you won't be able to do some of these missions till you level up and get better gear. However, once discovering a location, you can start the quest and fast travel back to finish. Initially though, travelling in certain areas can only be done underground through the metro system as areas are blocked by debris. There are usually several ways you can complete a mission, which will affect whether you gain good, evil or neutral karma. Some things are not entirely clear, however, as sometimes doing good will trigger a bad result, so save often in case you want to reverse decisions. Guides and walkthroughs are unable to provide all the possible ways you could perform many of the quests. The Wasteland is a completely open world to discover as you wish.
The currency is bottlecaps or goods you can earn or find in containers or on dead bodies. You can then buy or trade with stores or travelling caravans. You never know where the latter might be at any given time and stores are not plentiful. Tradesmen also have different amounts of caps, which will prevent you from selling to them over their limit. This also shrinks the number of places you can trade. The only way around this is to buy their repair service or enough goods to raise their limit, however later your own repair capabilities will be greater. Their goods also change, so they might not have an item you passed up on when you meet them again.
Leveling up is based on gaining experience points by killing people, mutants, wild animals or performing certain functions like hacking. Once you gain a level, you will be given a number of skills to choose from. If you do not have the DLC Broken Steel, which raises the leveling to 30, your limit is level 20. There are several ways to increase your skills, but the choices are so many you will not be able to become proficient in everything without having the DLC. It therefore requires careful consideration about what skills you need to raise to a high level. You can really only concentrate on four or five tops and will inevitably be weak in some areas. There are several layers to this; one called S.P.E.C.I.A.L., which is addressed when you read a book as a baby in the vault, skill points distributed when you level up, and one choice of a Perk immediately after this. Points can be redistributed while in this screen, but not in game. You can also increase skills by finding readable books and bobblehead figures, which are hard to find in this huge world.
Although the graphics may be what a nuclear wasteland should look like, it can be a very depressing and gray world. There is often little color in the game as there is no greenery at all. However, in saying that, the environments are also exquisitely detailed in all of their bombed out state and the rendition of character faces is simply awesome.
There are quite a few weapons to chose from and each has a level of damage it can do. You can also find or buy schematics, which will enable you to make guns and explosive devices. A type of slow motion is available, but often this is not very accurate and recovery from this mode called VATS is quite slow, making it hard to dodge attacks if the enemy is close. Everyone in the Wasteland is pretty jaded and hard and most will attack you on sight, however, you can find some companions as well as a dog who will love you despite your faults. You'll just have to scour the Wasteland to find them.
On a final note, this game can be buggy in so many ways that it's not possible to cover them all, so you will have to research solutions as they come up. Although my game did randomly crash a few times, it was not frequent enough to warrant installing user mods to fix it. However, this might be the only way for people having greater difficulties. I did have to use a console cheat at one point in the game. In Little Lamplight you have to do things in a specific order, but after trying all of the recommendations, I still couldn't get the dialogue option needed to progress.
I have not played the earlier Fallout games and apparently this one is quite a different formula with more shooter aspects added. I've read that Fallout New Vegas is closer to the originals. However, I confess that I'm about half way through that one and it's been sitting on hold for quite some time as I found it very boring and irritating in some ways. The consensus seems to be fairly evenly split on which one people prefer so it gets down to a matter of personal taste. Fallout 3 encourages exploration of the world with things to find, whereas New Vegas offers little reward off the beaten path or outside of the quests.
UPDATE MAY 2015: As with many older games, Fallout 3 was not designed to run on multiple core systems or technology that is well beyond its time. However, there are guides provided by users to help you get this game running if you are experiencing problems. This is an example Steam Community