The first thing you should do is to get your friends to help you get rid of these things. Getting off of addiction, in the beginning, is usually the hardest part, so getting support the whole way through is extremely important.
It can also help to find healthier alternatives. For example, some people who have been addicted to eating rubber have tried chewing gum instead.
For some people, just going to the doctor and learning the health risks that their addiction have is enough to convince them to change. It all depends on the person of course.