So some friends and I are interested in playing some for the first time and don’t really have a clue where to start. I stumbled on Mouse Guard just by the artwork a few days ago and fell in love. Looks like it would fit the bill nicely. What exactly do we need to start from scratch? Just the book? Dice? Is the more expensive boxed set necessary?
Sorry if this has been asked a million times. Browsed through the last few pages and searched without really finding much. 
I have no first-hand experience with Mouse Guard, but I’ve asked the same question. The box set is nice, but it is not required. The boxed set is a recent release; the game’s been around (and has been much enjoyed) for a while. You’ll need some six-sided dice.
Okay, thanks! So, all we really need is to grab the book from somewhere and raid Risk and Monopoly for dice? Excellent.
Edit:
I already downloaded the character files stickied on this forum. Looks like that’s about what comes with the box anyway…
The book is definitely required, the box is definitely nicer if you can manage to get it.
In addition to book and dice… don’t forget to bring your imagination! That’s really the key component.
You will need to understand the game, that’s all. And accept that probably is not the same kind of game you’ve been playing so far. What experience do you have? That can be important.
Technically, you need the book, at least 10 six-sided dice and a few character sheets. Don’t make characters yet. Just use the premades. And navigate through the forum and read a lot.
Enjoy.
Pretty much zero xp with this sort of thing. I’m sure rpg video games do not count. Other than that, just a couple onlie mafia games and a couple fan fiction forum RPGs that went sour quick.
Ten dice, read the book through a couple times, pre made character sheets, hang out with you guys. Anything else?
If I say “imagination” again, someone will hit me with -1D for repeating myself. 
It sounds like you are on the right track. Alexandro’s advice about using pre-gen characters and adventures that come with the book is also good. You’re likely to come back to us after your first session and say “We had a good time, but this GM/Player Turn thing doesn’t make sense”, and things such as that. You’re at least slightly less likely to come back with those questions if you start with the starter materials.