. . . cinch down bolts. Not too tight.
The single most important piece of advice when using a stamped steel valve cover with side bolts. I have wrenched on many a car where the valve cover bolts were cranked down so tight that they distort the cover - creating a bow in between the bolts - causing the cover to leak even more!
You're also spot on with the use of RTV and/or Formagasket . . . it has to be allowed to setup or one just squeezes it out when the bolts are snugged down.
On the heavier aluminum valve covers - held on by two central studs - there is less chance of distortion from over tightening. With a clean and straight head/cover I have had good luck with Copper Coat on both sides of the gasket. This stuff was designed for use on Head Gaskets - but I use it everywhere.
When I do encounter pitting I use Permatex with a sharp putty knife to fill the pits. Which gets me back to a smooth surface.