Ideally, there should be formulas or parameters that a country or its central bank has to strictly adhere to when it comes to matters on the national currency especially on determining the number of them on print or circulation. However, realistically speaking, most countries are not following the standard all because the political leadership can easily print more paper money especially in times of distress or problems...and which can be producing more problems especially into the next generations. Therefore, this is not the question of HOW but by WHOM.
I have no doubts that how much money is to be printed should be a technical question and not one decided by politicians and the evidence for this can be found in all periods of history, but make no mistake politicians will not give out this power since it allows them to tax all the population with the inflation tax, this is one of the many reasons why I support bitcoin, no one can decide how much bitcoin can be created in a day or a year and if anyone decides to do so then they will be fork bitcoin and they will have to convince people to use their chain which no sane person will ever do.
