Is there a preferred side (right or left)in which Increases/decreases are done on?
What are you making? Can you link to your pattern?
Well, it depends. Some require both sides, some one or the other, some in the middle. So a link would help.
I don’t have a link I’m just freestyling a pattern with scraps.
Well then, the increases or decreases are made to shape the knit piece, so it depends on where you would like that shaping.