The cheapest way to get into town is onlocal bus #119 (daily 5am–midnight; every 15–20min; journey time 25min), which stops frequently and also ends its journey outside Dejvická metro station.
How You can buy the Ticket?
You can buy your ticket from the public transport (DP) information desk in arrivals (daily 7am–10pm), or from the nearby machines or newsagents (just near by the bus stop). If you’re going to use public transport whilst in Prague, you might as well buy a pass straightaway.
Turkish 
English 