Hmm, here in Poland we use right alt plus a letter to make the diacritic version of it, e.g. alt+a = ą (the left alt functions like in other keyboards).

It is probably easier for language that doesn't have multiple diacritics for the same letter.

In Poland we have only one such letter: z. The problem is solved by using 'x' for the other (less frequently used) diacritic type:

alt+z = ż

alt+x = ź