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!