Arriving in a city where you don't know anyone is fine for the first afternoon and exhausting by the third. A local guide fixes the specific problem of not knowing where to go: one person who actually lives there, walking around with you, answering the questions a map app can't - which places nearby are worth it, which aren't, what's normal to order.
What a local guide is actually good for
Not the landmarks - you can find those yourself. What a guide is actually good for is everything a search engine handles badly: the neighborhood that's quietly good but has no reviews yet, the restaurant locals actually go to instead of the one with the queue out front, how to get somewhere without three transfers on the metro. It's local knowledge, rented for an afternoon.
How this differs from a tour company
A tour company sells you a route and a group of strangers. A guide booked directly is one person, on your schedule, adjusting as you go - if you want to skip the third museum and just sit at a café for an hour instead, that's the whole plan changed with one sentence, not a group vote. It costs less than most guided tours once you're past a single person, and it scales to exactly what you actually want to do that day.
What to arrange before you land
Message a couple of days ahead if you can - guides with good reviews get booked out during peak travel seasons in popular cities. Say roughly what you're interested in (food, history, nightlife, just walking) so they can plan a route instead of guessing on the day, and confirm the meeting point somewhere easy to find, like your hotel lobby or a well-known landmark.
Making the most of the day
Tell them honestly what pace you want - some people want to cover as much ground as possible, others want three good stops and a long lunch. A guide who knows that upfront plans a much better day than one guessing your preferences as you go. If you're landing somewhere new soon, check who's available there before you book flights around a fixed itinerary. Know your own city well? Become a local guide and get booked by people landing there.
