Minecraft wiki entry for Superflat_survival, associated text: Look up villager trading charts and trade with villagers to get resources you couldn't get anywhere else.
Use an infinity bow over an mending bow. Arrows are hard to farm until you have a skeleton grinder (Regular mob farm).
Don't kill the wandering trader without checking the trades, some trades are required to progress further in the game.
If you need leads, kill the llamas but not the wandering trader. A donkey can carry more items than a llama.
After getting a campfire from a fisherman's trade, you can break it without Silk Touch to obtain charcoal and craft torches.
Never fight an iron golem without armor, it can kill you quickly.
If you find a zombie villager, don't kill it, instead, trap it and make sure it doesn't despawn.
Avoid raids until you have an enchanted iron sword/diamond axe and at least full enchanted iron/diamond armor.
Use the right enchantment:
Sharpness: illagers, creepers, witches
Smite: zombies, skeletons, drowned, phantoms
Bane of Arthropods: spiders, endermites
It is possible to get diamond armor from zombie and skeleton, but it takes a long time.