Naples has an extensive public transit network, one of the biggest in Italy, serving more than 4 millions of inhabitants in the metropolitan area.

There are several comprehensive transit maps in internet, but most of them aren't updated. You can find an updated map of the Naples metro network here: http://www.napo...

Here is another useful map, showing metro lines (line 1 in yellow, line 2 in blue), funiculars and tram lines (in green):

You can also ask for maps at the tourist offices in Capodichino airport arrivals terminal, Napoli Centrale/Garibaldi train station, Galleria Umberto (near the San Carlo Opera House) or in Piazza Plebiscito. There's also an online bus map for Naples (not updated)..

 UnicoCampania have recently made available some handy PDF maps for their various bus, metro, train and train services. There are five in all - including one with suggested ways for getting between key points around the city. To download one or more, start from the new 'Maps' link on the first of their English pages, here: 

If you own a smartphone, you can see all the Naples network with metro, trams, funiculars and bus lines and stops (with timetables) with googlemaps+.

You should also download this very useful app on your smarthphone: Gira Napoli. It shows in realtime the departures at the stops of every lines of the Naples public transport network (buses, metros, trams, funiculars). It shows also a lot of other useful tourist informations.

Download link for android:

Download link for Iphone:

Basic Unico Napoli transport tickets (biglietti) are valid for 90 minutes on all forms of transport within the city, cost 1.10 euro, and can be purchased at Tabacchi (tobacco shops) or newsstands. A daily pass is about 3 euro. A different ticket is needed to reach Pompeii and Sorrento by train. You must validate your ticket as you enter the bus or train station when using it for the first time. Having a ticket that has not been validated is the same as not having a ticket at all. Yellow validation machines are not always obvious - you may have to look for them. Inspectors regularly stake out the connections between stations to make sure that travelers have valid tickets. Having an unvalidated ticket will get you a spot fine of 37-100 euro.

Useful transit hubs are Piazza Garibaldi for trains and buses and Aeroporto Capodichino, the main airport for Naples. Most bus and trolley lines go to the main Garibaldi/Napoli Centrale railroad station, and many go past Plebiscito (Castel Nuovo, Royal Palace , Opera House).  Please be careful as there are many pick pockets on the stations platforms and the hustle and bustle is an easy distraction so take care and be aware.

Useful bus and tram routes include:

R2 (bus) from Garibaldi train station to Piazza Municipio and Piazza Plebiscito through Corso Umberto (Headway of 8-12 minutes, but this bus line is often crowded).

Tram line 1 (less crowded and speedier than rhe R2 bus ) from Piazza Municipio (near Hydrofoils and Cruise ships Terminal) to Piazza Garibaldi (Central Station) and Centro Direzionale (the bigger skyline in Italy) through Via Marittima and Corso Garibaldi. Trams headway is ten minutes and travel time is about 10 minutes to Piazza Garibaldi, 20 minutes to Centro Direzionale.

2M (bus) from Museo Archeologico Nazionale to Museo di Capodimonte.

R4 (bus) from Piazza Municipio to Museo di Capodimonte, through Piazza Dante and Museo Archeologico Nazionale.

140 (bus) from Piazza Municipio to Cape Posillipo trough Chiaia and Mergellina.

The Alibus is a special bus running a circular route with only 3 stops: Capodichino airport, Garibaldi train station, and Piazza Municipio across from Molo Beverello port. Buy tickets onboard for 3 euro and validate in the machine. Many suburban bus lines also leave from in front of the train station, or from a terminal a few blocks south of the Maritime Station along the waterfront.  These can take you to Amalfi, for example. The Circumvesuviana trains to Pompeii and Sorrento leave from the main station, but in a separate downstairs area.

The Metro is currently being extended to better serve the historic area, but this huge project involves lots of archeology, and may take years to complete. At present, two metro lines depart from Piazza Garibaldi (under the Central Station). The line 1 (trains every 8 minutes) goes to University, Toledo, Piazza Dante, the National Archeological Museum, and then up the Vomero Hill, while the line 2 (trains every 12 minutes) goes from Garibaldi train station westward to Pozzuoli, through Chiaia, Mergellina and Fuorigrotta (San Paolo Stadium).

Another transport option is the funicular lines, there are three lines running from historic center to the Vomero Hill, and one line running from Mergellina to Posillipo hill. A funicular is basically two special rail cars, each attached to opposite ends of a long cable, use for climbing and descending hills. As one goes up hill, the other goes down, and they cross in the middle. Three of these lines run from the hilltop Vomero neighborhood to various parts of downtown; the fourth runs from the bottom to the top of Posillipo. The funiculars can be a time-saver. For example, take the funicular from near the Royal Palace (up Via Toledo about one block) to Vomero, then walk a couple blocks to the other funicular station and go downhill to the Metro stop — easy access to the Phlegrean Fields, Mostra d'Oltremare, Pozzuoli, or even downtown Naples.

You can reach Sorrento , Capri, Ischia and other islands by boat from the Molo Beverello Maritime Station at the foot of Municipio. Tickets can be purchased on a walk-up basis. Multiple companies and boats depart each day about every 30 minutes, subject to seasonal availability.

You can reach Pozzuoli and the volcanic Campi Flegrei area (sandy beaches, lakes and archeological sites) by Cumana commuter train, that departs from Montesanto every 20 minutes.