For our money, Markun Shuttle is probably the cheapest fastest and easiest way for individuals or smaller groups to get from the airport to the city centre if you don't already have arrangements on arrival (which is why we usually end up taking it). Reservations can be made in advance, but there is always at least one van just opposite the arrivals exit, and we've never waited more than 10-15 minutes for it to leave on the half-hour journey. Drop off service to your hotel, apartment or private accommodation is only €9 per person.