There are some decent books on Amazon that can help you. I've found it's a combination of everything and I mean everything. Your attitude about your speech is important. For me negative thoughts breed stuttering. Sometimes I literally have to force myself to be positive about everything including my speech. Then find some technique that works for you. That can be whispering, sing-song talking, chewing gum while you talk (it might take effort to find what works for you), but once you find it just stick with it and don't give up till you are fluent. I jump on the phone every day and call business and ask them when they close or think of something just so I don't let fear paralyze me.