Paris has an efficient metro system that can take you almost anywhere in the city. A single ticket costs €1.90, but a better option is to buy a pack of 10 tickets for €16.50. Taxis are also readily available but can be quite expensive, especially during rush hour. Renting a bike is a fun and eco-friendly way to explore the city, and costs around €5-€10 per day.
If you have more time, consider visiting the charming villages around Paris such as Chantilly, Auvers-sur-Oise or Fontainebleau. Another option is to spend a day at Disneyland Paris. If you have a shorter trip, consider skipping some of the busier tourist spots such as the Eiffel Tower, and instead focus on the city's hidden gems and local neighborhoods.