You'll need a juicer. You can make a smoothie instead using a blender, but the consistency will be different, and you'll probably want to add some ice.
This recipe is modified slightly from one my naturopath gave to me. She called hers "Green Lemonade".
3 or 4 leaves KaleWash everything. Cut items only if necessary to fit into juicer. A decent juicer will handle the apples whole without you having to peel or seed them. If you have a variable speed juicer, all the better. Juice the leafy greens on low, the 1/2 lemon on medium, and the rest on high. This will make about 2-3 cups. Serve and exclaim, "Oh, that looks disgusting yet is wonderfully delicious!"
1/3 head Romaine Lettuce
2 medium Apples
1 inch piece of Ginger, peeled
3 or 4 Celery Stalks
You can drink this juice every day, though for maximum benefit you'll want to vary your greens, particularly your leafy greens. Try chard, spinach or other leafy greens, and substitute cucumber or green melon for the celery.
If you can only manage to make this once per week, save it for the day after your most exhausting day. It will help to cleanse and recharge your body.