Beginner survival loop
Move and evolve weapons, kill Tyranid synapse creatures before the swarm goes Berserk, and treat a red screen as an Ork Waaagh!.
Walk, shoot, pick up the gems, keep the horde on one side. That part is the poncle feeling Auroch keeps describing. It lasts until a faction trait turns on.
Kill a Tyranid synapse creature before you fall in love with your clear. While it lives, nearby Termagants and Hormagaunts go Berserk. When it dies, they drop into a short stunned shock. If the screen starts going red, that is an Ork Waaagh: more bodies, and the ones already there frenzy. Do not stand in the lane a Skaven Ratling Gunner just painted.
Pickups sit by the faction lights. A Melta-bomb wants a kite. The Purple Sun will hit you. The long version, with the Bell of Doom and Hellfire Ammo in the same breath, is how a run actually goes.