Scrubbing your produce is super important. Since you are extracting the juice from the entire veggie, you want it as clean as possible You will want to buy a veggie wash or make your own.
I just use a simple scrubber like this:
Just wash and scrub your veggies. Much of the nutrients is left in the peel of the fruit or vegetable. To maximum the nutrients scrubbing as opposed to peeling is great. If you are not buying organic, I would peel the veggies. Oranges, lemons, kiwi, etc. still need to be peeled prior to juicing.