The scams you are talking about are likely from the random people that stand around and ask you if you want a taxi, or the black 'limousine' cars. If you take a normal Dubai RTA Taxi (Called Hala Taxi), then you will not be scammed as it runs on a meter. Just head to the sign that is clearly marked as 'taxi' at all terminals, and make sure you get on the cream coloured (red roof, yellow roof, blue roof or pink roof) Hala taxis. Over there, they may also try guide you to the black 'limousine' cars, but just refuse and say I want a Hala taxi. Alternatively, as others have said, use the Careem app (my preference), or Uber. They have seperate specific pick up points (also signage points them out at all terminals) for the ride sharing apps.