Public transport intimidates everyone for exactly one week, and then it becomes the easiest part of life abroad. Start with a mapping app that covers your city with live transit directions; it will tell you which bus or train, which platform, and when. Most transit authorities also have their own official app, which is worth installing for ticket purchases, disruption alerts, and route maps.
The part that actually trips up newcomers is not navigation but ticketing culture. Some systems make you validate or stamp your ticket before boarding, some use tap-in and tap-out cards, some run on trust with roaming inspectors and serious fines for the unticketed. Learn your city's rules on day one, because ignorance is not accepted as an excuse anywhere.