For general thinking about someone or something:
* Penser à: This is the most common and direct translation.
* Example: Je pense à toi. (I'm thinking of you.)
* Avoir quelqu'un/quelque chose à l'esprit: This means "to have someone/something in mind."
* Example: J'ai ton anniversaire à l'esprit. (I have your birthday in mind.)
For thinking about someone with fondness or concern:
* Penser à quelqu'un avec affection: This emphasizes the positive feelings you have for someone.
* Example: Je pense à mon grand-père avec affection. (I'm thinking of my grandfather with affection.)
* S'inquiéter de quelqu'un/de quelque chose: This means "to worry about" and implies concern.
* Example: Je m'inquiète de mon amie. (I'm thinking about my friend with worry.)
For thinking about something in a particular way:
* Réfléchir à: This means "to think about" something more deeply or critically.
* Example: Je réfléchis à mon avenir. (I'm thinking about my future.)
The best translation will depend on the specific context and the nuance you want to convey.