Find a reference point. For road positioning, if you think you're in a good position confirm it with your instructor by asking them if you're ok. Then look over to the right of your windscreen and notice where the centre road lines "meet" the windscreen so to speak. It's usually easiest to notice where it lines up to a point of the window wiper.
You can also use the same method to line the edge of the curb up with a point on the left window wiper in order to be able to pull up to a curb consistently.