The most common way of forming the plural is with the ending -s (exactly as it is in English; finally something simple).
Examples plural with -s
le livre
les livres
book
books
le chemin
les chemins
way
ways
le garçon
les garçons
boy
boys
le papier
les papiers
paper
papers
la maison
les maisons
house
houses
la rue
les rues
street
streets
la table
les tables
table
tables
la fourchette
les fourchettes
fork
forks
As you have probably noticed the final -s
is only written but not voiced (there are again exceptions to this rule). To know whether the thing in question is in singular or plural (which is often of some importance) there are several possibilities of differentiation, for instance by pronouns and articles. Following some examples with articles:
Examples
Je mange une pomme.
Je mange des pommes.
I eat an apple.
I eat apples.
J' achète
une chemise.
J' achète
des chemises.
I buy a shirt.
I buy shirts.
As mentioned before the final -s is voiced, when a vowel or a mute h follows this final -s. Listen to the following sentences, there is a difference in the pronunciation of the final -s.