Hunger & Cold will be your most immediate survival concerns on a newly created character.
It's worth mentioning in this game mechanic guide that hunger or exposure to cold can kill the player, in addition to damage taken from monsters or falling. Falling damage has become far less lethal in the current version of the game, and gravity varies from planet to planet but this doesn't seem to depend on planet size.

Monsters can be hunted for raw alien meats with a bow or hunting knife. There are currently three tiers of bows available in the game, wood, iron & steel. Alien meat can be cooked at a campfire which the player can craft without a crafting table, but there are several other types of cooking stations available in the game that serve the same function as a campfire. Cooked alien meat fills the hunger bar by a small amount, whereas most food recipes fill it completely and provide a healing buff. For example the basic healing food for Humans is Burgers and for Apex it's Battered Bananas. Even bread is superior to meat for filling your hunger bar and only requires 2 wheat, plus a cooking station which is needed for all other cooked food items besides meat.

Each player begins the game with two types of farmable crop seeds. You will get 3 seeds of each type to begin with and can acquire more seeds by harvesting crops, each harvest has a chance of producing 1 or 2 seeds. Harvesting Wheat will sometimes produce plant fibre instead of wheat, so it's beneficial to have large amounts of wheat planted to keep you supplied with bandages. Every race starts the game with Wheat seed and one other racial crop seed, other seed types have to be found from the environment. Some crops can be found growing wild and others can be found in NPC farms near villages or found in chests and other containers. As of v. Angry Koala, trees can also be planted and farmed for wood which can eliminate the need to mine coal ores. So its necessary to have a home base where you can do your farming. As you can see in the above screenshot I simply created a flat surface with dirt blocks to farm on, you need two block layers under trees or the wood and seed will fall beneath your platform. It's far easier to build a platform out of dirt blocks than leveling terrain for your farm.

As mentioned, exposure to cold environments can also kill the player and every armor item has a warmth value which protects against the cold.
The player starts with two clothing items that collectively provide 2 warmth and no armor value, this is not enough warmth value to protect the player from cold night air on most planets.
You can warm up by standing next to a campfire, but two torches are almost as good as a campfire for warmth, placing a campfire next to your bed will keep you from freezing while sleeping.
Sleeping in a bed is currently the only way to pause gameplay as your hunger bar will not advance while you are in a bed, so if you need to run AFK make sure you use a bed.
The Steel armor set is the first to provide enough warmth to protect the player from cold night air, but it's still not good enough for snow planet biomes.
You can craft a set of Leather armor with a very high warmth value, but sadly the armor value on this set is very low since v. Angry Koala update. Leather can be acquired from monster drops when using a bow (or hunting knife) to hunt, there is a small chance you will get leather instead of raw alien meat. Still the Leather Armor set provides enough warmth to allow you to travel to Snow planet biomes. Wearing only the Snow Infantry hat with your iron armor set may provide enough warmth to survive a snow biome.

The airless environments of moons and asteroid belts are also very cold, you need at least the Durasteel armor set to protect against this level of cold. You will also need to craft and equip the Survival System backgear to survive airless environs, so you will need lots of Durasteel bars at tier-4.