Plural of a noun is generally formed by adding s/es to the singular form of noun.

eg. ball-balls, place-places, bed-beds

words ending in o/ch/sh/ss/x take es

bench-benches, potato-potatoes, fox-foxes 

* nouns ending in y are made plurals by dropping y and adding ies

eg. lady-ladies, fairy-fairies

However, if y follows a vowel in the noun, plural is made by adding only s. 

eg. bay-bays, monkey-monkeys

* the following nouns ending in f/fe take ves in plural form after dropping f,fe

calf-calves, half-halves, knife-knives, leaf-leaves, life-lives, and similarly for loaf, self, sheaf, shelf, thief, wife, wolf.

However, words hoof, scarf and wharf can either take s or ves in plural form

hoof-hoofs/hooves, scarf-scarfs/scarves

Other nouns ending in f/fe take s in plural.

eg. handkerchief-handkerchiefs, cliff-cliffs

* some nouns change vowels in plural form.

eg. woman-women, mouse-mice, foot-feet

* collective nouns remain singular if referring to a group but take plural form if referring to a number.

eg. The jury is reviewing its verdict.               

 The jury are reviewing their verdict.

* some nouns are always plural.

eg. spectacles, pants( consist of two parts), other words like outskirts, stairs, savings etc.

However, some words are in plural but are singular in meaning

eg. news, billiards, rickets

* compound nouns take plural form according to the last word.

eg. girl-friends, house wives, lady bugs

If man or woman is the first noun, then both the nouns are made plural.

men drivers, women drivers

If compound noun is in the form noun+ preposition+ noun, then the first noun takes plural form.

eg. mothers-in-law