Follow the first two
Alien movies. That is, get strong actors, including those who have worked extensively in theater. Also, use actors' appearance and age to amplify atmosphere. For example, for the cast of the first movie, Ebert writes,
QuoteNone of them were particularly young. Tom Skerritt, the captain, was 46, Hurt was 39 but looked older, Holm was 48, Harry Dean Stanton was 53, Yaphet Kotto was 42, and only Veronica Cartwright at 30 and Weaver at 29 were in the age range of the usual thriller cast. Many recent action pictures have improbably young actors cast as key roles or sidekicks, but by skewing older, Alien achieves a certain texture without even making a point of it: These are not adventurers but workers, hired by a company to return 20 million tons of ore to Earth.[17]
https://en.wikipedia.org/wiki/Alien_(film)#CastThis technique is mostly lost to contemporary producers, and only because they need attractive A-listers to increase ticket sales.
For any cast members playing military personnel, follow this move from the second movie:
QuoteActors who played marines were asked to read Starship Troopers and undergo military training, which included running, lifting weights, learning salutes, marches, deployments, and maneuvers, for two weeks. Cameron wanted the marines to train together so that they would form bonds that would show on-screen. Sigourney Weaver, William Hope, and Paul Reiser were absent from training because of other obligations, but Cameron felt that this suited their characters as "outsiders" in the film.[11]
https://en.wikipedia.org/wiki/Aliens_(film)#Cast