The first hour after arrival
Drive a slow loop within 1 mile of the property. Find: the nearest supermarket (Tesco/Sainsbury's), the nearest petrol station, the nearest pharmacy, the nearest takeaway you'd actually trust. 30 minutes invested saves you 6 weeks of mild confusion.
Local nuances that surprise outsiders
In Glasgow people queue at the bar. In Newcastle 'mate' is gender-neutral. In Brighton parking is genuinely impossible — don't even try.
Apps that help
CityMapper for any city it covers, Citymapper Maps elsewhere, Google Maps' offline maps downloaded for your whole stay area in case data goes down. PayByPhone or RingGo for parking.