A poet has already answered for us this question: En présence du Ciel, il fautcroire ou nier.
Croire Il s’en croit beaucoup = He thinks a great deal of himself.
A l’en croire il a eu tous les prix = If he is to be believed he won all the prizes.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "croire" in a variety of sentences. We hope that you will now be able to make sentences using this word.