The first few nights in 99 Nights in the Forest decide whether a run goes well. Here is what to focus on.
Day 1: wood, food and the fire
Cut wood and feed the campfire first. The fire is your safe zone and your progress: upgrading it opens more of the map. Grab berries and hunt rabbits so hunger never becomes a problem.
Night 1: stay in the light
The Deer is immortal and hunts in the dark. Do not try to fight it. Stay near the fire, keep your flashlight ready and point light at the Deer to drive it off.
Upgrade the campfire to level 2
This usually unlocks the first missing kid, the Dino Kid, guarded by five wolves. Bring a weapon, eat before you go, and clear the wolves one at a time.
Craft defences before the raids
Cultists raid your camp at night. Build defences around the fire and keep crafting better weapons as you find scrap and materials.
Spend Diamonds wisely
Redeem the codes for free Diamonds. Poison Master (200 Diamonds) is a strong cheap class. Save for Big Game Hunter or Cyborg (600 Diamonds each) for long runs.