I need to fix my intonation on my Epi LP Jr. I can't hit harmonics as easily and the natural harmonics sound bad...(That means its time for intonation right?)

So I need to know how to do it. I know it has to do with the little black screws/nuts/bolts/whatever you call them on the back of the bridge.

Which way do I turn them?
How do I know how much to turn them?
All that jazz...

No, it's because the pickups in the Epi LP Jr's are weaker than tin foil pickups.