Gazareth's suggestion is spot on, you really want to get it on a decent gas analyser or you're just guessing.
I've never seen any guideline that says, all the way in and then 3 turns out is about right, or anything like that.
My recollection is that anticlockwise is leaner though. If you look carefully you can see a slot (or maybe a pair of holes above each other if it's an early one) on the side of the tube which the CO screw sits inside. As you unscrew the screw, anticlockwise, more of the slot is opened up and more air goes in = leaner.
I think the version on the 1.3 engine, the 2e3 does work the way you say, so maybe that's where you've seen that?
Book spec is 1% +/- 0.5% CO IIRC.