I used to have this problem. it used to control me and hold me back, but I've learned how to control it. It takes a degree of concentration at all times to maintain control (or oyu will probably revert) , but it can be done.
There is a theory that people with stuttering problems form words on the right side of the brain instead of the normal left side, and these words must cross over to the left side before they can be spoken out loud. There is a crossover delay, and the problem is the result of trying to say the words before we are able to. We are literally getting ahead of ourselves. The most practical solution is to slow down so the information can transmit.
1. slow down. Most of your problem comes from talking too fast. It's not like people are going to walk away when you're talking, so take your time. I generally speak at about 90 words a minute, which is slightly slower than normal. (most people speak at 100-120 wpm) You can practice slowing yourself down by speaking ridiculously slow, dragging out sylables. (preferably do this alone-- try reading out of a book out loud) Once you're comfortable with speaking that slow, speed it up slightly and get comfortable with it. Keep speeding it up until you can speak with control at a slightly slower than normal rate.
2. If you get stuck on a word, don't force it. Basically, if you try to force your way through you're going to end up trying to talk without any air in your lungs, and oyu can't do that. If you feel stuttering coming on, just relax, take a breath, and say whatever you were about to say again.
3. Speak from your diaphram. (your voice should feel like its projecting from down low in your gut, not high up in your throat) You have much much better control, also try to lower your voice pitch if you can, and keep doing that until it becomes a habit. When you're speaking at a lower pitch, it's harder to talk fast, you have more control, and as a bonus, chicks find it sexy.
4. Keep your voice on inbetween words. If you do this, the momentum will keep you going. It's sort of like singing, except there is no melody and you are not altering your pitch.
5. easy onset. Don't emphasize the first sound at the beginning of a sentence you're speaking. This wastes your air and you won't have enough. Relax and start your sentences calmly.
I hope this helps, it did for me.
