Learn About the Fallout Series
If you bought Fallout 4 on a whim or if you just want to refresh your memory (Fallout 3 came out in 2008, after all), spend today and tomorrow catching up on the lore.
Fallout 4 is going to be populated with various characters, factions, weapons, and locations. And many of them are going to have a backstory. You probably won't be able to get to everything in a day but it's worth getting the big plot points nailed down.
The Fallout Wiki is the encyclopedia of Fallout information. It's a great place to start. It'll also be a great place to go if you want to know more about something in Fallout 4. You can also watch this video from IGN below if you learn better visually.
The Wasteland is a huge place that will captivate you. And while some of you might want to start from scratch, others will want to be armed with information so that everything going on around you makes at least some sense.