The earliest conscious suicidal ideation I can remember was sometime in grade school, around 3rd or 4th year, so I was 9-10 y/o. I was at my grandparents apartment, 8th floor, and it was recurring - every time I visited, I stared at the balcony, envisioning myself jumping, also thinking about leaving a goodbye letter. I don't remember what it would contain, but I think it was very childish and petty, blaming everyone, especially my older brother for me doing it. It never went beyond passive ideation though.
All the way through middle and high school I was also on-and-off passively suicidal, depressed, but it never went farther than that. Third year of uni was when I began thinking about death constantly, by the end of it I was researching methods (even visited this site for the first time!), but never attempted. Closest I got was trying to get to the roof of a university building, and it was closed. Even if it wasn't, I highly doubt I'd jump, also it was like 6 stories... Ok so basically I never attempted.