Formal:
* Preste atenção: This is the most direct and formal translation.
* Fique atento/a: This literally means "stay attentive," which also conveys the idea of paying attention.
Informal:
* Presta atenção: This is a more casual version of "Preste atenção."
* Escuta: This literally means "listen," but it also implies paying attention.
* Liga: This means "turn on" and is used when you want someone to focus their attention on something specific.
* Espera aí: This literally means "wait there," but it can also be used to tell someone to stop what they're doing and pay attention.
Other options:
* Concentre-se: This means "concentrate," which implies focused attention.
* Tome cuidado: This means "be careful," but it can also be used to tell someone to pay attention to what they're doing.
The best way to choose the right expression depends on the situation and your relationship with the person you're speaking to.