1small lemon(or half of a large one; no need to peel it)
1inchknob of fresh ginger (no need to peel)
If your juicer has two speeds, start on low. Run the cucumber through the juicer, followed by the celery and parlsey together to help prevent the parsley from flying around in the chute. (This is only an issue when using a centrifugal juicer.)
Switch the speed to high, then juice the apple, ginger, and lemon. I like to sandwich the ginger between the apple and lemon, so that it won't fly around in the chute or go into the pulp basket before it hits the blade of the juicer.
Stir the juice well, and then drink it right away. If using a centrifugal juicer, you can store the juice for up to 24 hours in the fridge in an airtight container. If using a masticating juicer, you can store the juice in an airtight container in the fridge for up to 72 hours. Either way, make sure you fill the container all the way to the top, so that no air is left inside to help slow down the oxidation process.