One of my closest friends tried attempted suicide last year. The first thing obviously was to make sure he survived. We don't live in the same city, so that was a very long and stressful day for me. Fortunately, we have mutual friends who I could reach. (I was the only one he texted before the attempt.)
Anyway, after he was well, I never really pressured him to talk about it. I, and others, convinced him to talk to a therapist. After I believe a week or so, he just randomly opened up and we talked for hours. This happened a few times. But I always tried to not pressure him into opening up, and kept our friendly banter and everything. I never wanted him to feel that something between us changed because he tried to take that route. I'll still call him names and roast him, and he'll clap back. That's just our dynamic. I think people often overcompensate, and end up making things worse.
That paragraph turned out to be much less structured than I had hoped. It's just hard to put into words what to do. I guess, just try to be a good friend. Whatever that means for you. Be there for them. Talk to them. Don't pressure or guilt them into doing anything. Don't guilt yourself into behaving differently. Be compassionate if they do open up, but don't force them. Just be like you usually are, grab a drink maybe, and have a good time with them.