Rules for Writing Pinyin

For whatever reason, this morning I finally (after three years!) decided it was worth trying to learn the correct way to write pinyin. That is, assuming you know the correct syllable and tone, how do you write it? If, for example, you are given "huai" 4th tone -- is it hùai, huài, or huaì? (the answer is huài.) I found the very concise rules here. For my own reference I am going to blatantly copy them:

A and e trump all other vowels and always take the tone mark. There are no Mandarin syllables in Hanyu Pinyin that contain both a and e.

In the combination ou, o takes the mark.

In all other cases, the final vowel takes the mark.