Best way to set any chain is to pull the suspension up until the countershaft, swingarm pivot, and axle are all in a straight line. I usually do this when greasing the suspension linkage which I do immediately with any new-to-me bike (.ie the shock is off), or you can use a cranking tie-down, or a fat friend. This will put the chain at its tightest point. Give it 3/4" of slack. Then release everything and figure out where and how you want to measure slack in its "relaxed" state. I generally end up with about 3 fingers between the chain and swing arm at the end of the chain guide.