Light is survival
A lit cave is a survivable cave. Flare early and often, and treat darkness as the enemy.
Call everything
Resupply, targets and heavies. Callouts are free and they are what separates a team from four players.
Use the databases
Do not hold 67 equipment entries and 80 creatures in your head. The equipment database and creature database are the reference that makes planning quick.
Leave a margin
Finish missions with something in reserve. Surplus is the buffer that turns a bad spawn into a manageable one.