It's not easy finding your way around a foreign city, or a foreign language.
Sometimes you will get lost, make mistakes or cross boundaries you didn't realise were there.
In those moments, it's handy to have a few phrases to hand, to apologise, to smooth any feathers you may have unintentionally ruffled, and leave a favourable impression instead of a poor one.
Let's start with the situations where you know that what you're doing might disturb someone else, like trying to squeeze past them, to get off a bus or train.
You can request their cooperation, in advance, with '¿Con permiso?' or '¿Me permite?', or you can begin your manoeuvre, then apologise, with 'Perdón'
'Perdón' is also a good way to get someone's attention, if you require assistance e.g.
'Perdón ¿Podría decirme, donde está la estación de autobuses?' - 'Excuse me, could you tell me where the bus station is?'
If you do happen to tread on someone's toes, as you squeeze past, 'Lo siento' (literally 'I feel it') is probably the commonest way of saying 'I'm sorry', and you can say it to anyone, without having to consider whether the situation, or their status, requires 'tú' or 'usted'
You DO have to consider that, if you want to use 'perdóname' (tu) and 'perdóneme' (usted) and 'discúlpame' (tu) or 'discúlpeme' (usted).
If you've really upset someone, though, you could always try 'mil disculpas' (a thousand pardons)
I like to pick words apart, and the etymology, or evolution of 'disculpar' is an interesting case.
From the original Latin word 'culpa', meaning guilt - 'DIScúlpame' means 'unguilt' me = relieve me of my guilt = pardon me.
The word 'culpa' also means guilt in Spanish so, if someone begins to apologise to you, for a bump, or jostle, but it's really your fault, you could take the blame with 'No, yo tengo la culpa'
Your parents and grandparents may have told you that good manners cost nothing, but it's definitely worth spending a little time, learning a few exculpatory (another lovely word ;-) phrases, although I hope you don't need them.
¡Hasta la próxima!