Typically I hang for about 7 to 10 days, what I look for is the small stems snap when bending in half, at this point the trimmed sugar leafs that are still part of the bud will feel very crunchy and dry. If you don't dry enough then you will end up with buds that smell like wet grass and possible mold. When you first put in jars be sure to open every day and shake around to get fresh air in or even take out of jars completely for a few hours at a time each day.
This method has worked best for me, my first harvest I ruined because I put in jars too soon