Installing the transport apps before you fly is one of those five-minute tasks with an outsized payoff. Landing in a new country tired, possibly without mobile data sorted, is the worst moment to be searching app stores and creating accounts. Set up the official transit app of your destination city, a good mapping app, and download the offline map of your city while you are still on home wifi.
The benefits go beyond convenience. Many transit apps let you buy tickets digitally, which rescues you when the airport ticket machine rejects your foreign card or the queue is long. Route planners with live updates also protect you from the classic newcomer mistake of standing at a stop for a bus that has been rerouted or cancelled.
A couple of practical notes: some local apps require a local phone number or payment method to fully register, so do what you can beforehand and finish setup after getting your SIM.