@polotek@social.polotek.net Hey! 18 years industry experience here. I have never been taught how to estimate projects, formally or otherwise. What little I know about it is from trial and error.
When asked for an estimate, I compare it to something similar I've already done, and just kind of guess. System knowledge plays a part too. Like, if I know I have to touch some eldritch horror of a class, I'll add time to the estimate for that. So, I guess you'd say I have personal guidelines, but they're informal/instinct based.
I am not at all confidant in my estimates.
Also, my team does not do any kind of retrospective on estimates - we never go back and say "why did this take more/less effort than we expected?" Without that kind of reflection, I find it very hard to learn and improve.