One trick to remember when smoking sausages is to keep the temperature below 170 degF so you don't render the fat. You're trying to smoke, not cook. (...although you can do that later.)
There's a temperature window:
---Start off drying your sausage. Smoke on wet sausage causes a bitter taste, "they say." Vent wide open, 100 degF until it dries and a sticky pellicle forms.
---You did use cure #1, right? (Don't smoke without it.) Set the temperature above 140 degF while smoking, high enough to reduce the chance of botulism but cool enough for good smoke uptake. Smoke for the desired length of time (2 to 4 hours). I use an Amazin' tubular smoke generator. Works great. I had poor luck with chips.
---Then raise the smoker temperature to at most 170 and monitor internal meat temperature until it hits 150 - 155, to kill any possible trichanae. However, if you are using an electric smoker, be aware that the temperature control usually isn't that good. Mine cycled between 2 degrees below and 10 above the setpoint, so keep the setpoint lower. If you have to, finish heating in your kitchen oven. (...but check it, too. Some ovens also are lousy at temperature control.)
I recently bought an Auber PID controller, which controls to a much tighter range than the usual off/on control. At $180, it cost more than the original smoker (!), but it's worth it to me.
One more trick for tender casings: keep a pan of water in the smoker, to keep the heat moist.
Best of luck,
el Ducko
SausagesWest.com