as of about the last week... i don't use much ice.
Since the water level is 1/2" above the bottom hole of the stem (for my setup), the buoyancy of the ice counter-acts the draw and increases the resistance
So i only put enough ice to cool down the water and just deal with the resistance for the first 15-ish minutes.
I also find that I can taste the flavor a bit better when it's not SUUUUPER cold.
aside from that... see the links that KwiKwi posted and you should be set. I had been smoking for about a year (successfully, i might add), then I watched SamB's video and it brought it from good to great. Then Jilly put hers out and it's spot on as well, just a different explanation process.