Formal:
* À ce soir: This is the most common and formal way to say "see you tonight."
* On se voit ce soir: This is slightly less formal and means "we'll see each other tonight."
Informal:
* On se retrouve ce soir: This is more casual and means "we'll meet up tonight."
* À plus tard ce soir: This is very informal and means "see you later tonight."
In the context of a goodbye:
* Bonne soirée: This means "good evening" and can be used as a way of saying goodbye.
You can choose the best phrase based on the level of formality and the specific situation.