We usually walk around the city since almost everything is near.
Although if you may need to catch a bus to go to some places.
Leões (Arts School) - City Center - António Gedeão Residence - Colégio Pedro da Fonseca (Pedagocical School): You can catch bus number 23 or 24
There's a bus working everyday in city center. The ticket is 1€ per day and you can use the same ticket the whole day
This bus, Linha Azul (numbers 51 and 52), is very useful if you are carrying shopping bags, if you want to go to the train or bus station our if you are just super lazy and don't feel like walking around.
Very easy to catch, you can fin it in Praça do Giraldo, Largo Luís de Camões or anywhere in city center where you see a blue line on the ground