The thing about growing up with a Norwegian grandfather is that you assume everybody has a cheese slicer and egg cups. Turns out that one of the things American immigrants left behind in Europe were egg cups. I was reading an article on Lifehacker about how Americans eat soft-boiled eggs, seeing as how there is no such thing as an egg cup in the US. It was only then that I realized why a British friend who lives in Hawaii asked if I could get egg cups for him.
In every hotel I've been in in Europe, they serve soft-boiled eggs for breakfast. That is to say, they serve a hot egg that is still nearly raw, or a hot egg that is nearly hard. I therefore rarely eat soft-boiled eggs in hotels. But they do have egg cups (and teaspoons) for the eggs. And I have egg cups at home. Any complete set of dishes also includes egg cups here in Europe.
Now for some etiquette on eating a soft-boiled egg:
I learned by watching my Norwegian grandpa who had been a sailor for many years. I was quite proud of myself when I mastered lopping off the pointy end of the egg with a knife creating a "hat", like he did. Salt and eat the egg white in the "hat", then salt the rest of the egg and eat that.
Turns out that's the vulgar way. The in-polite-company way to open a soft-boiled egg is to crack the top of the egg with the back of your teaspoon, and peel the shell of the "hat" portion off. Then salt and eat.
All of this is of course easier to do with an egg cup.
Do add salt. Some people add butter. The taste of butter dominates too much for my liking, but I do like herbal salt on my eggs.
Oh, the perfect way to soft-boil an egg? Who knows. Many years ago I happened to win an egg cooker in a lottery (to my delight, as it turned out) and even that thing needs a bit of tweaking so I get my perfectly boiled egg: Solid white, runny yolk.