Once you have begun to teach your dog the basic command "leave it" make sure you practice your command when you have no need to use it. Your dog will be more successful because it will be easy to do. That's a good thing. You want his response to the command "leave it" to be an automatic head turn towards you.

If the only time you practice is when he has picked up a chicken bone from the ground, you and your dog will not be successful. 

This is not a substitute for structured training sessions.
Click here for a video on the first steps of training your dog to  "leave it".
Click here for video on teaching your dog to leave items on the floor.

Contact your local force free dog trainer on how to teach your dog to "leave it".