The priority for all first time visitors is to get an overview of Paris.
Free stuff:
- view the Eiffel Tower from the Trocadero (best pictures)
- visit parks and gardens such as Tuileries and Luxembourg
- stroll around the Marais district or on the Champs Elysées
- stroll arond the seine banks
- visit large department stores like Galeries Lafayettes or Printemps
There are also plenty of guides and tours to be booked, these can take you in a very short time around the city and see major sites.
For example:
- Eiffel Tower & Level 2 Viewing area
- Escorted Half Day or Full Day Tour of Paris
- Hop On Hop Off Double-Decker Bus
- Private Tour - 90mins ? by Taxi or Hire Car Good idea if time is short and you arrive or depart during weekends etc
There are several web sites that allow to book online local tours and activities and pay online with credit card: