Last updated in version 1.13.8 of Fallout Shelter on October 12th, 2018.
Welcome to the Fallout Shelter FAQ! There are a lot of common questions that get asked over and over, and there are also many hidden and unintuitive mechanics in the game, so I've put together a guide/FAQ. If you're brand new to the game I would strongly recommend reading through the help section in-game first. It covers a lot of the basics which I don't bother covering here for that reason. To access it tap the Pip-Boy icon in the bottom right, then tap the wallet-looking icon (above the gears). This opens the VDSG, and near the top is a help tab. The game will run in the background as you're reading, but if you do it in a brand new vault before dragging dwellers in then you won't have to worry about resources draining or anything.
If you've come from reddit, please check the first section before posting. I've included incredibly common questions there. Otherwise if you have a specific question or just want to browse use the section break down on the right to find things. If you want to link to a specific question just mouse over the question number to have a link icon appear to its left, then click that to generate a URL for you to copy.
If you notice any typos, or more importantly any incorrect information, please let me know so I can rectify the problem. As I imagine most traffic here will be from reddit, you can message me there. If you feel a question should be added or you've done some testing and found out something useful, also feel free to let me know so I can make an addition. I'll make any additions at the end of a section (or if a new section at the end of the FAQ), that way the numbering system and any references to them won't get messed up. I will do my best to keep this updated.
There's also a Fallout Shelter Discord that everyone is welcome to join. Whether you've got a question you want answered, you want to show off your vault, or you want to be a part of a community around the game then come on over.
A huge shoutout to DanK___ who wrote the original FAQ that was stickied on r/foshelter. I copied a lot of stuff that hadn't changed from them. Another big shoutout to ShardisWolfe, SlowbroGGOP, and GOD-WAS-A-MUFFIN, all who have been huge contributors on r/foshelter and who I borrowed a lot of stuff from to write this. Thank you as well to anyone who I linked to that did testing and/or wrote content. I credited everyone where I could when I linked to anything. A bunch of screenshots don't have names, as I copied them from DanK___'s FAQ where they were uncredited, though I assume they were their own. There's no way I'd have all the content in this FAQ without all the help from many different people.