Get a car with a straight horizontal window line. Old Mercedes, Volvo Bricks, etc.
This makes parking much easier, as you can subconciously aligne the car with straight lines in the surroundings of your parking space (in man-made environments, there are always straight lines somewhere. Think the line where a wall meets the pavement or some reference lines on the ground).
In a tight garage, the wall should do. If you paint a horizontal line on the garage wall at waist hight, this should be even easier.
Assuming you don't want an old brick and already have a modern car, have a look if you can program the right mirror to swivel downwards when going into reverse - a lot of cars can do this so that the rear mirror shows the curb when parallel parking. (Else, just adjust the mirror manually.)
Then pick a point on the garage wall as a reference stop point. If your garage wall is to far away, paint a line on the floor as a curb simulator or mark spots for the tyres. If the right side tyres both are on their markings, car will be perfectly positioned.