T tag onto Smokin's good advice,there are a couple times I might preheat.
If I am wanting to smoke someting,a little,and not do a lot of cooking.I may turn it on down around 180ยบ,just until the smoke starts and turns kinda clear.
I'll then add product like small fish,or chicken breast fillet,peeled-hardboiled eggs,etc.
The cooker is usually not much warmer than the Fl sun would make it.