Obi-Wan: Remember, a Jedi can feel the Force flowing through him.
Luke: You mean it controls your actions?
Obi-Wan: Partially, but it also obeys your commands.
The Force is strong with Luke, even before he becomes a Jedi. It obeys his commands and controls his actions and allows him to fly the X-Wing more skillfully than he could without the connection to the Force. With the Force as his ally, Luke can sense (sub-consciously at this stage in his training) the future and this allows him to avoid the station defences and the TIE fighters.
As Qui-Gon says of Anakin:
He can see things before they happen. That's why he appears to have such quick reflexes. It is a Jedi trait.
Vader is also very sensitive to the Force and knows what a pilot can do when the Force is with him. He can recognise that the pilot of this X-Wing is a Force user, albeit an untrained one.