Well, Taxis are usually easy to spot. In England they have the word TAXI written on them, for a start. In New York they're famously yellow. In Guyana their registration numbers begin with the letter H.
The first taxi companies started up in London and Paris in the 17th century, and in London the horses to pull them were kept in the district of Hackney. London Black Cabs (the ones you can hail) are still officially called Hackney Carriages.
If you're in India you might be lucky enough to travel in an auto-rickshaw; in Mackinac Island a taxi-sleigh; and in Venice, of course, the taxis are aquatic. There are flying taxis, too.
They're all very useful when you're lost, tired, or you've met bad weather.
But what's even worse than it raining cats and dogs?
Spot the frippet: taxi. The term taxicab was coined by Harry Nathaniel Allen in New York. It's short for taximeter cabriolet. Taximeter comes from the French taximètre, which is made up of the Mediaeval Latin taxa, which means tax or charge, and the Greek metron, which means measure. Cabriolet is the French for a little skip, and is from the Latin capreolus, a wild goat.
So there you are: look out for someone enjoying a ride in a wild goat charge-measurer today.