Choosing between the passé composé and imparfait

passé composé

imparfait

an action that interrupts another

"Je lavais la vaiselle quand tu m'as téléphoné"

a short, one-time action

je t'ai téléphoné hier

an action that starts after another

"Je lavais la vaiselle, puis (then) tu m'as téléphoné"

a sudden action

"La tonerre a éclaté soudainement"

Some common words that show we use the passé composé:

tout à coup, soudainement, quand, lorsque,

An action with a definitive ending

"hier, j'ai lavé la vaiselle" (hier means it ended, we aren't still washing the dishes)

Talking about time

"Il était 6h00"

describing something or someone

"Il faisait beau dehors"

A long or continuing action

"Quand j'avais 6 ans, j'ai cassé la jambe"

(being six years old is a long action, and breaking your leg is a short, one-time action with an ending so it is PC)

repetitive actions

"Je me levais à 6h00 chaque matin."

an action that gets interrupted

"Je lavais la vaiselle quand tu m'as téléphoné"

doing the dishes got interrupted by you calling on the phone

Quand j'avais six ans nous sommes allés au parc. (the passé composé implies that they only went to the park once when they were six years old)

Quand j'avais six ans, nous allions au parc (the imparfait means that they went habitually, multiple times to the park when they were sic years old)