In compound nouns and noun phrases the final element usually takes the possessive form. If plural compounds pose a problem, use “of.” Examples: a cookbook’s recipes my daughter-in-law’s profession, but the professions of both my daughters-in-law.
In proper names or where there is no clear possessive meaning, the apostrophe is omitted. Examples: Publishers Weekly, CLASS Christian Writers Conference, Department of Veterans Affairs, a housewares sale.
When neither an “s” nor an apostrophe alone look right, avoid the possessive and use
“of” instead. Example: For the love of Jesus.
Possessives, such as hers, yours, and its, have no apostrophe. Example: The dog scratched its fleas. “It’s” is the contraction for it is. Example: It’s going to rain today.