As well as a bus network, Lisbon also has a tram network; the Companhia Carris de Ferro de Lisbos (Carris) operates all transport except the metro. Buses and trams operate from 5/6am to 1am the next morning; there are some night bus and tram services. Check the Carris website for timetables and route maps or alternatively you can pick up a transport map from tourist offices or any of the Carris kiosks around Lisbon.
A single ticket will cost €1.45 on board or €0.85 if you buy a bilhete unico de coroa (BUC, a one-zone ticket for the city centre). You can buy these pre-paid tickets beforehand at the Carris kiosks – the most handily at Praca da Figueira and at Santa Apolonia and Cais do Sodre metro stations. The Carris kiosks also sell one day Bilhete Carris/metro tickets; these cost €3.75 and are valid for buses, trams, funiculars and the metro for 24hrs.
Tram stops are marked with a yellow sign either hanging from a lamppost or from overhead wires. If you want to experience something historical in your transport catch Tram 28 from Largo Martim Moniz or tram 12 from Praca da Figueira through the narrow streets of the Alfama. These trams are of a small few that are the original tram lines in the city, manufactured during the 1930s and 40s. Tram 28 in particular twists its way through the labyrinth of Lisbon’s ‘Old Town’: beginning in Graça then moving down to the Alfama, through to Baixa then up through Chiado to Bairro Alto, finishing at Campo Ourique, taking you by many of the city's most famous locations.
A great way to save money, especially if you intend to do a lot of exploring, is to get a Lisboa card. It offers unlimited use of public transport, entry to all popular museums and attractions and up to 50% discount on tours, cruises and other admission costs. You can get these cards at all tourist offices, including the one at the airport. Prices vary, depending on how long you want yours to last. 24/48/72-hour ones cost €15/26/32 respectively; there are children’s ones available at €8/13/16, the condition being that the child must be aged from 5 to 11 years.