I cut all hard ends off and save for a stock, you can also use the ends of what comes out of the juicer for a stock...you just have to boil, and strain it.
I frist clean all with tap water and then soak in a large bowl of purified water for 10-15 mins and then juice it.
Some use the pricey veggie wash ( hint you can you 3% hydrogen peroxide in a spray bottle...just make sure your peroxide doesn't contain ANY stabilizers in it.
This will highly oxygenize the veggies and helps remove toxins.
This is a good method to use if you cant get organic.
Health food store have Food grade Hydrogen Peroxide at 35% ...PLEASE look in to that because it is very concentrated and you have to dilute it with distilled water for use.