Relatedly, if a friend approaches you with suicidal feelings, never ever ever try to talk them straight out of it. It is quite likely that they will consider you as simply not understanding them, and shut you out - possibly pretending that all is fine, when it really isn't.
Always try to genuinely understand their feelings and reasoning. Treating suicide as something that is always and inherently wrong, is more likely to hurt them than to help them.
Make sure that they understand that you're willing to listen without judging, even if you might not always immediately understand their reasoning, and even if you might not agree with them.
In a few cases I knew, it seemed the warning signs were that the person mentioned things like "yeah I would never kill myself" seemingly out of the blue. And then one went and registered to buy a gun. (Which was eventually used for the act). You are right that these are described more as "feelings" not just direct verbal statements of the intent to commit suicide.
* have you thought of a plan for how you would do it?
* have you taken any actions on that plan?
The farther down they get that list, the more concerned you should be. emergency intervention if they Yes all four.
Many people have dark thoughts but have a fear/preservation instincts that protects them from rash inclinations. But once someone starts acting on their thoughts, they need close attention from someone quick and strong enough to intervene. As noted, though, knowing someone's state requires their willingness to honestly share it, so caregivers need to be trustworthy and be trusted.
Giving someone hope and a way forward can help them walk back from the edge, but being manipulative or deceptive or coercive can push them over.
I took an emergency suicide first aid course a couple years back, and to this day still carry around the pocket-sized "workflow" in the wallet in the hopes I never need it.
That been said, one of the most important things I took from the course was the need to have the person with the experimental thoughts to agree to stay safe. That is, to agree not to harm themselves for a pre-allotted timeframe. You’re not convincing them not to do it, but instead delaying their feeling of having to do it now. This time gives you both the ability to seek resources to help each other through the crisis.
As said above, be supportive of the person. Hear them out. Pushing them away or making light of the situation is not something that that will benefit anyone. You may not agree with them, but you must understand in order to help them through this period in their lives.
Be honest and tell them you don't know how to help - but agree to seek out help with them. Perhaps they just need someone to show that they are cared for...
tl;dr get the individual who is experiencing suicidal thoughts to agree not to harm themselves for six hours (a completely arbitrary number) so that you both can seek resources for help. DO NOT try intervention unless you are trained to do so - you could make things much much worse...
Always try to genuinely understand their feelings and reasoning. Treating suicide as something that is always and inherently wrong, is more likely to hurt them than to help them.
Make sure that they understand that you're willing to listen without judging, even if you might not always immediately understand their reasoning, and even if you might not agree with them.