Prague taxis are very shady, and should be taken as a last resort - there's plenty of public transport (but always buy a valid ticket). If you have to take a taxi, order one from AAA. They are the most honest and reliable I found in the city, and they have English speaking dispatchers. Just tell them where you are and they'll send a taxi, normally within 10-15 minutes.
Tel: 14 0 14 222 333 222; www.aaa.radiotaxi.cz/en
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