Here is a useful summary on writing good requirements by Scott Sehlorst on the Tyner Blain blog. Scott derived and refined the list starting from Pragmatic Marketing's Requirements that Work Seminar.

Attributes of good requirements:
based on Pragmatic’s List (1-8) + Two Three Four More

Necessary => Valuable
Concise
Design Free
Attainable
Complete
Consistent
Unambiguous
Verifiable
Atomic
Passionate
Correct
Stylish

Scott provides links to articles on each attribute that provide additional details.

Chuck