How do you reach the best way to heathrow airport terminal 3 from stratford in london?

The best way is to take the London Underground: Central line from Stratford (heading towards Ealing Broadway or West Ruislip) and then change at Holborn onto the Piccadilly Line (heading towards Heathrow Terminal 5) and exit the Underground at Heathrow Terminals 1, 2, 3. Follow the signs to terminal 3.