While virtually every recipe/instruction I've seen for the SI says not to pre-heat, I have a friend that has what is probably an original model #1 who gave me the following instructions when I made salmon for New Years and it came out excellent!
* Put in a couple ounces of soaked chip or block fruit wood
* Turn the smoker on and let it get up to temp and smoking
* Put the salmon on the top rack for 35-40 minutes
Take care to not overcook... even 5 minutes over can dry it out. The instructions were for ~ 3 pounds of salmon. Thinner pieces and/or individual slabs need less time.
I did wash/dry my salmon first, let it sit for 30 minutes, and then seasoned. It was excellent.