Something that really helped me quit once was not only effective, but free (aasuming you still have some cigs) - the last night you plan to smoke,
light a couple
of smokes, and put each one out when it is half gone. Then the next day, when you quit, and feel the urge to smoke or get stressed, take one out and hold it in your hand like you are smoking. You can even puff on it, there will be some residual smoke taste. Just don't light it!