Going to a public place. Start speaking to random employees in the stores. Ask questions about no particular merchandise. You just want to start a conversation with these people.
Joining a speech course at school. This will conquer your fears once and for all. In order to pass the class you will need to stand up in front of the class and speak your brains out. This should eradicate your fears of stuttering in public. If you fail the course because you got too nervous then take the course again.