1. To show possession, ’s is used with singular nouns  and plural nouns not ending in s.

Ex:  the actor’s chair, the child’s, the crew’s quarters, the children’s room

2. A simple   « ’ »   is used with plural nouns ending in  «s».

Ex:  the Adams’ family, the aliens’ ship, the gladiators’ battle, the dinosaurs’ nest

3. Other names ending in  «s»  can take   «’»   or   « ’s».

Ex:  Antonio Banderas’ house or  Antonio Banderas’s house, Mrs.  Jones’ husband or

       Mrs.  Jones’s husband

4. With compound nouns, the last word takes the «’s»:

Ex: The Prince of Belair’s  program.

     It can also be used after initials:

Ex: the VIP’s  limousine

NOTE: The possessive ending is mainly used for people, countries or animals. 

But it can also be used for:        

- in time expressions:

Ex: today’s newspaper - for planes, trains, cars and other vehicles.(but the “of”      construction is safer…)

Ex:    the car’s wheel (or) the wheel of the car

- for ships and boats:  

Ex:    the ship’s anchor

-for expressions of money  +  worth:

Ex:     twenty dollars’ worth of movie tickets.