Do not rush the next biome
Each biome assumes the previous biome's gear fully upgraded. Sailing in under-equipped costs you your inventory and a long boat trip back. Fully upgrade before you go.
Food is your health bar
Your maximum health comes almost entirely from the three foods you eat. Always carry the best food you can produce — three good foods roughly triple your effective health.
Build a portal before you explore
Place a portal at home and carry materials for a second one. Connecting a new biome back to base lets you ferry ore and return after death immediately.
The rested buff is free power
Sitting by a fire grants a regeneration and stamina bonus that lasts a long time. Re-apply it before every expedition and before every boss fight.
Learn the stamina economy
Running, swinging and blocking all draw on the same pool. Retreat to recover rather than fighting at zero stamina, where you cannot dodge or block.
Base near water
Most ore and progression travel happens by boat. A base on the coast with a sheltered dock saves a great deal of hauling.
Prepare the boss summon in advance
Gather boss summon materials before you need them and build a small shelter near the altar so a failed attempt does not cost a long walk.