What to bring, what to say first, and why one problem per appointment is not a rule to resent.
A fifteen minute consultation sounds short and it is, so here is how the ones that go well tend to go.
Bring three things. Your identity card, every medicine you are taking in its own box rather than from memory, and any letter or result from another clinic or hospital, even an old one. A doctor who can see what has already been done starts the appointment several minutes ahead.
Say the main thing first. Not the history of it, not what your neighbour thought, the main thing. There is always time to come back to the story, and a consultation that reaches the real reason in the last two minutes is the one that ends with come back next week.
Book the right length. Fifteen minutes is for one thing. If you have three, or a condition that has been going on for months, the thirty minute appointment costs more and is worth it, because two short appointments cost more than one long one and take twice as long to arrange.
And say if you do not follow something. Doctors here are told to explain twice and to write the important part down, but nobody can tell from the outside whether an explanation landed. Asking is not rude and it is not wasting the appointment. It is what the appointment is for.