20) Don’t send all of your dwellers into the wasteland at the same time.
Only send as many as you can afford to lose. Don’t send anywhere near all of them. Be sure that you can still manage to keep your vault afloat with the ones you leave behind. If you send them all, and then they die, and your leftover dwellers are killed off by disasters or raiders, then you’re screwed. Unless your last dwellers are pregnant women, because then they won’t be able to die!
19) Merge rooms together.
Merge two of the same identical room to make a double room, and merge three of the same identical rooms together to make a triple room. If they don’t go together right away, then that is because they are at a different upgrade level, meaning that you should then upgrade them to equal levels.
18) Upgrade your rooms for more efficiency and better output, but wait until after merging the rooms to do that.
If you merge the rooms first, then you will be able to upgrade the rooms for a whole lot less caps spent per room. The first upgrade to a single room will cost 250 caps but the first upgrade to a triple room will only be 500 caps, or 167 caps per space. That is a far better deal.
17) Grow your vault SLOWLY.
Don’t load it up with as many dwellers as possible right away or they will present a huge drain on your water, power, and food, which are your three resources. Grow your vault slowly and add one dweller per resource room at first (yes, including 2x and 3x resource rooms) so that you have the most resources and the least dwellers to use them, allowing you to drive your resource bars FAR into the green.
16) Let dwellers sit outside of the vault until you need them.
This includes dwellers coming back from the wasteland or new dwellers who do not yet have a residence. You can let them sit outside of the vault and they will not use any resources. Their happiness will not decrease either, nor will it count toward your overall total, so let them sit out there for as long as you want.