could someone explain the light cycle to me please

[psteve]

In veg, you want NO MORE THAN 6 hours of DARK.
In flower, you want NO LESS THAN 10 hours of dark.
Most people I know flower at about 1/2 of the finished hight. IE: if you want 4ft plants when they're finished, you should change to the flower cycle when your plant reaches 2ft.
This is not true for every strain. Sativas may grow taller, and some indicas may not stretch as much, but 1/2 is a good starting point.