How to properly use the belt tensioner bolt when changing belts on a civic?

I found this great answer, the second one: http://www.justanswer.com/honda/1k3fw-change-alternator-belt-2003-honda-civic.html

On part (7) and (8) it says to turn the belt adjusting bolt counter-clockwise to loosen the belt. But how do I gauge the bolt and belt tension after I put the new belts on? How do I know when I've screwed the bolt enough, too much or too little?

Thank you

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