The Alien star believes the key to her 40-year career is knowing how to "read" a script and see whether there's a good story, rather than a huge part for her, and also her penchant for mixing up the types of movies she makes.
"I've worked hard my whole life to be offered different things," she said.
"People always want to give you the same role you just played - I want to mix it up.
"What has helped me is that I know how to read a script. I never turned down a role because it wasn't a lead - if the script is good, it's going to be a project worth seeing."
The 66-year-old will next be working on a number of sequels to James Cameron's Avatar and thinks them being commissioned is a sign of the changing nature of Hollywood.
"I'm getting ready to do four more 'Avatars'. Back in the day you would never want to do a sequel - that would be very declasse. Now, everyone wants a franchise."
Weaver believes the rise of social media has dramatically changed fame, telling Glamour magazine: "It's a different animal now - there's less privacy.
"Social media is great, but I'm glad no one said to me, 'This is part of your job'. But for some young actors, I think it must be."
While the Avatar movies are big-budget blockbusters, Weaver's most recent work has been on smaller-scale productions Tomboy, A Revenger's Tale and A Monster Calls.
She enjoys the challenge of low-budget films.
"I love working with young directors. I like how creative people get when they don't have a lot of money. It's fly-by-the-seat-of-your-pants acting."
