One of the things that makes the French language so trying at times is l’accord.  Agreement in gender, number and person between subjects and verbs, adjectives, nouns, articles, pronouns, etc.  Today, we’ll talk about the first kind.

1. Mes filles aiment leurs poupées Disney.  (My daughters love their Disney dolls.)
2. C’est nous qui sommes sur la photo. (That’s us in the picture.)
3. Beaucoup de filles portent des jupes. (Many girls wear skirts.)

The general rule is that the verb agrees with the subject of the sentence in number and person.  In other words, singular subjects with singular verbs and plural subjects with plural verbs plus 1st person subjects (je, nous) with 1st person verbs, 2nd person subjects (tu, vous) with 2nd person verbs and 3rd person subjects (il, elle, on, elles, ils) with 3rd person verbs.  We can see this in the first example above.  However, when the subject is the relative pronoun qui, the verb agrees with the pronoun’s antecedent.  The second example above shows us this where we use ‘sommes‘ because the pronoun’s antecedent is the first person subject ‘nous‘.  Another example of this would be C’est moi qui ai fait la cuisine.  (It was me who did the cooking.)  In French, unlike English, the subject can come after the verb…so be careful.  This is the case with:
C’est dans cette ville qu’habitaient mes parents quand ils étaient plus jeunes.  (My parents lived in this town when they were young).

If the verb has several singular subjects (compound subject linked with ‘et‘ (and), the verb is made plural.  For example,
Mon père et ma mère se sont mariés en juin 1975.  (My father and my mother were married in June 1975.)

Now, for some special situations.

When the verb has subjects of different persons, you make the agreement like this:
Toi et moi aimons la cuisine française. (You and I love French cooking.)
2nd person + 1st person subjects take ‘nous‘
Mon mari et moi aimons le cinéma. (My husband and I love going to the movies.)
3rd person + 1st person subjects take ‘nous’
Votre mari et vous aimez les expositions d’art.  (You and your husband love art expositions.)
3rd person + 2nd person subjects take ‘vous‘ 

When using a compound subject linked with ‘ou‘ (or), the verb is either singular or plural depending on the meaning of the sentence.  For example:
Mon mari ou ma fille fera la cuisine ce soir.
So, the verb is singular when meaning ‘one or the other’.
Le passeport ou le permis de conduire sont des pièces d’identité. (Passports and driver’s licenses are identity documents.)
And here the verb is plural when meaning ‘both of them’ (in English, we usually use ‘and’, not ‘or’ here.  But, the French apparently like ‘or’ better.)

When using a compound subject linked with ‘ni…ni’, the verb can either be singular or plural.
For example:
Ni son père ni sa mère n’est professeur. (Neither his father nor his mother is a teacher.)
Ni son père ni sa mère ne sont professeurs. (Neither his father nor his mother are teachers.)

When the subject is a collective noun like peuple, foule, groupe, ensemble, bande, orchestre, équipe, majorité, troupeau, etc., the verb is usually singular even though they have a plural reference.
Ma famille est d’origine irlandais. (My family is of Irish origin.)
Le public a hué pendant dix minutes. (The audience booed for ten minutes.)

But, be careful: when the collective noun is followed by a plural noun, the verb can be plural as the noun is considered to be similar to a ‘quantity noun’ like douzaine, kilo, etc.  For example:
Une foule de touristes visitaient Versailles. (A crowd of tourists visited Versailles.)
La majorité des américains préfèrent la bière au vin.  (The majority of Americans prefer beer to wine.)

When the subject includes beaucoup de, peu de, trop de, assez de, combien de or la plupart de, 10% de, 50% de, etc. plus a plural noun, the verb is plural. This is the case of the third example at the beginning of this article.
Beaucoup de filles portent des jupes.
46% des électeurs démocrates ont voté pour Hillary Clinton en 2008. (46% of Democrat electors voted for Hillary Clinton in 2008.)

But, be careful: if they are followed by singular nouns, then the verb is singular.  And beaucoup, la plupart, etc. when standing alone take plural verbs.  For example:
Les étudiants n’ont pas bien travaillé.  La plupart n’ont pas réussi. (The students didn’t work hard.  Most of them did not pass.)

Finally, when the subject includes le seul qui, le premier qui, le dernier qui, etc., the verb can agree with the subject of the main verb or it can agree with the le seul, le premier, le dernier, etc.  For example :
Vous êtes le seul qui puissiez m’aider.
Vous êtes le seul qui puisse m’aider. 

In short, just make sure your verb agrees!!