Rule for adding "and" or hyphens between numbers that are spelled out fully in text

I was always taught, in American English, to use "and" only with compound numbers such as "three and three-quarters." Wikipedia also mentions this:

Note that in American English, many students are taught not to use the word and anywhere in the whole part of a number, so it is not used before the tens and ones. It is instead used as a verbal delimiter when dealing with compound numbers. Thus, instead of "three hundred and seventy-three", one would say "three hundred seventy-three". For details, see American and British English differences.

And as ElendilTheTall said, hyphenate numbers between twenty-one and ninety-nine as well as fractions.

This is a common mistake made by Microshaft. There is no such thing as American English, there is English and there is wrong. 'And' is correct three hundred and forty-two = 342 three hundred point forty-two = 300.42 always the 'and'in numbers. Personally, I'm with the above = Hyphenate all compound numbers between twenty-one and ninety-nine.