Tram 28 is a great way to see the city, but it can get crowded during peak hours. Consider taking a taxi or an Uber if you're short on time. Lisbon also has an extensive network of buses and the metro that can take you to most major attractions. A day pass for public transportation costs €6.40 and can be purchased at any metro station.
If you have more time, consider adding a visit to the Belém Tower or the National Azulejo Museum. If you're a fan of seafood, check out Cervejaria Ramiro for dinner. If you have less time, skip Bairro Alto and head straight to Castelo de S. Jorge for stunning views. Don't forget to wear comfortable shoes - Lisbon's hills can be steep!