General:
* Avoir un(e) / avoir une: This is the most literal translation, used for general situations like "have a good day" or "have a nice evening."
* Prendre un(e) / prendre une: This is more informal and can be used for things like "have a look," "have a drink," or "have a seat."
Specific situations:
* Have a good day: "Bonne journée!"
* Have a good evening: "Bonne soirée!"
* Have a nice weekend: "Bon week-end!"
* Have a good trip: "Bon voyage!"
* Have fun: "Amuse-toi bien!"
* Have a drink: "Prends un verre!"
* Have a seat: "Assieds-toi!"
The best translation will depend on the specific phrase you are trying to translate.