Try reading
this. There are plenty more other guides on the internet so just google it and look. It's pretty risky and hard for most so if you're not good at cloning, get a friend or a trustworthy person to do it. Always ask for collateral or an equal pokemon to hold when you're making someone else clone and I'd talk to the person and stalk them for a few hours before letting them have my pokemon but that's me. :P