I'm sorry for your loss. That's a heavy thing to deal with, and to go through it three times is pretty brutal.

Suicide hotlines are still a thing. Exactly how they work and how to contact them will vary depending on your region. They're almost certainly in need of more operators, and while I'm sure they'll give you some advice for helping people going through it, I'm not sure what kind of experience you need to work or volunteer with them (again, that will vary with region).

I will caution you that it's an extremely difficult job. That's not to dissuade you from going out to help people - but to help others you have to help yourself first so you need to be aware what kind of toll that work can have on people.

Regarding my own suicidality and with men in particular there comes a fear of vulnerability. Suicide is one of the heaviest, most personal things a person can go through. Oftentimes our culture, or upbringing, or gender norms prevent people from opening up emotionally. Suicide is taboo and the suicidal often struggle with feelings of guilt, and talking about it brings in a fear of rejection or ridicule.

The advice I can offer is to try and foster an environment where people can open up to you judgment-free. If you're willing to be vulnerable around others that sets an example that they can be vulnerable around you. Hearing about suicide is also an upsetting thing, and if you have a history with several victims you might naturally be upset to hear someone is considering it a fourth time. If your feelings are explosive, try to rein them in - an outburst likely means they won't open up to you again.

Because the fear of opening up is real, it might be difficult to recognize the warning signs. This isn't a failure on your part, the victim is literally hiding it from everyone. Most people expect the suicidal to be depressed, but people will often socially mask their feelings by overcompensating with an appearance of happiness. However, if there is someone who you fear is considering suicide and is outwardly depressed, and then one day out of the blue they're suddenly fine - that can be a signal they've decided to end their life which somewhat paradoxically brings about a feeling of peace. In either case, when somebody starts giving away treasured possessions (sentimental, expensive, or things they use every day), that's a pretty clear warning.

I'd also advise you to check out some resources online. There are associations for suicide prevention and mental health in general that have some fantastic resources available to the general public. While not specifically what you asked for, here is a toolkit for people who have lost someone to suicide.

There is one more thing I'd like to add. It might be upsetting, but its intent is to give you peace of mind: you can't help everyone. That's not a cop-out or callousness either. In psychiatry there is a concept of resistance which implies a couple things.

First, a patient is likely to resist any psychiatric intervention - therapy is difficult, it can hurt you emotionally, and the patient's disordered behaviour is often a coping mechanism that they've learned to deal with their life - even if they want to be fixed they might not want to lose their coping methods or lifestyle.

Second, a therapist is unable to help a patient that does not want to help themselves. You can try every trick in the book, but if they're really not into it then there's no way to help them. That's not a personal failing on the therapist's part. Now technically in the case of suicide you might be able to point to how a doctor can force someone into a hospital if they're at imminent risk of suicide - but stripping someone of their autonomy and pumping them full of drugs until the danger passes is the exact kind of behaviour that would prevent someone from opening up again.

I am really sorry you're going through it. Don't beat yourself up, and try to remember them as they were before they got sick