General belief:
* Croire: This is the most common and general way to say "believe".
* Penser: This translates to "think", but can also be used to express belief in a less strong way.
* Avoir confiance: This translates to "have trust", and is used to express confidence in something or someone.
To believe someone or something:
* Croire à: This is used to express belief in something abstract, like a theory or a cause.
* Faire confiance à: This is used to express trust in someone or something.
Examples:
* Je crois qu'il pleuvra demain. (I believe it will rain tomorrow.)
* Je pense qu'elle a raison. (I think she's right.)
* J'ai confiance en lui. (I trust him.)
* Je crois au pouvoir de l'amour. (I believe in the power of love.)
* Je fais confiance à mon médecin. (I trust my doctor.)
The best way to choose the correct phrase depends on the specific context and the nuance you want to convey.