I like to clean all of the sealing surfaces with lacquer thinner and a microfiber cloth. If the surface of the heads is pitted around the water passages and depending on the style of the gaskets I will put a light application of RTV around the water passages. Then I run a bead across the front and rear valley rails about 3/8" wide from corner to corner. Then I put the gaskets in place on the heads and touch up the RTV in the corners if necessary. Then set the intake as carefully as possible to set it straight down. Then tighten the bolts in a criss cross pattern from the center outward in several stages. I just use Ultra Black RTV.