Everyone's first instinct is to hunt for their own city and see what it landed on. That is the one approach guaranteed to tell you nothing.
Straight lines and curved lines are different animals
The straight vertical lines are MC and IC lines — the longitudes where a planet was directly overhead or directly underfoot. They run pole to pole and they depend only on the time, which is why they are the most forgiving of a rough birth time and the easiest to trust.
The curved ones are AC and DC lines — where a planet was rising on the eastern horizon or setting on the western one. They bend because the horizon does. Near the poles they can loop and double back in ways that look like a drawing error and are not. Curved lines carry more of the chart's personality and less of its reliability, because they move much further for the same error in your birth time.
How close is close enough
Most practitioners work with something in the range of a few hundred miles either side of a line, and there is no agreed number because there is nothing to agree it against. Closer is treated as stronger. Somewhere between roughly 100 and 500 miles is the band people argue inside.
The practical consequence is that you should not read a map to the resolution of a postcode. A line passing forty miles from a city is, for every purpose you have, passing through it. If a reading depends on whether you live on the north or south side of a river, the reading is doing something the technique cannot support.
Crossings, and why people overrate them
Where two lines intersect, both planets were angular at once, and the tradition treats that as a doubling-up. Those points get called *power spots* by people with something to sell. They are worth noticing, and they are also unavoidable — with ten planets and four angles there are a great many crossings, and most of them are in the ocean.
A crossing is only interesting if you would have found both lines interesting separately. A Venus–Saturn crossing is not twice as good as a Venus line; it is a place where the tradition says ease and restriction turn up together, which in a real life usually means something slower and more serious than the Venus line alone would suggest.
The order to actually look
Start with the places you have already lived or spent real time in, and see what they sit on. This is the only calibration you will ever get: you know what those places did to you, so you can check whether the system's description of them bears any relation to your experience. If it does not, you have learned something more useful than a shortlist.
Then look at the lines rather than the cities — find where your Sun, Venus, Jupiter and Saturn lines run, and notice which continents they favour. Only after that should you go looking for specific places, because by then you are asking *what is on my Venus line* rather than *please tell me something nice about the city I already want to move to*. The second question is the one that produces the spiralling.