I've been asked on occasion, "How does someone get to be an Associate Editor for a journal like @ASNAmNat ?" Here's a brief thread explaining:

1) It's okay to tell the Editor-In-Chief that you are interested. Doesn't mean they'll pick you, since we don't want the AE board to get overly large and mostly seek to fill openings when existing AEs step down. But, it can't hurt. About 1/5 of our recent AEs got on by asking

2) Build a record as a thorough, thoughtful, constructive, and timely reviewer for a journal. The first thing I do when considering a new AE is check whether their past reviews were (mostly) on time and were high-quality (yes, journals record these data).

Your past reviews are evidence of your involvement and the level of care you put in. Also, being an AE requires faster turn-around that reviewing, so slow reviewers aren't likely to fare well. Sometimes I bend this rule for an exceptionally thorough reviewer (quality > speed)

But how, you ask, do you get asked to be a reviewer? Building a reputation in your subfield helps. If a student or postdoc, ask your PI to decline some reviews but recommend you instead, or co-review.

Or, contact an Associate Editor in your subfield in a journal you'd like to work with and let them know you are available. Editors-In-Chief don't pick the reviewers, the AEs do.

It is rare that we invite people to be AEs who don't have a record reviewing for us, and preferably publishing with us (at least, submitting). Submitting manuscripts to a journal conveys interest in that journal and its community.

Do we ever invite AEs who don't publish with us / review for us? Rarely, yes, but that's mostly when we want to branch out & diversify the AE board (geographically, conceptually, and other ways) beyond the pool of our reviewers/authors.

Publishing with and reviewing for us tells us you are part of the intellectual community the journal serves, that you have an interest in this journal in particular, and therefore have a stake in the journal's success. Or, tell an Editor directly by reaching out to volunteer

The difficulty we face is that often our focus on prior authors/reviewers limits the pool of people we might invite. So, we do welcome suggestions and volunteers (though again, depends on our needs for new AEs)

When a current AE steps down, I always ask them for suggestions for a replacement, people they leaned on regularly for quality reviews. I always emphasize we want to improve our AE board diversity, and encourage the AEs to look at @DiversifyEEB and related lists for inspiration

So to sum up, to become an AE, establish a role as author/reviewer with a journal, then let your interest be known.

PS, we tend to ask people to become AEs right around when they go up for tenure, at the earliest, with some exceptions