if wipers "hop" and "skip" a lot of times you can take a Crescent wrench and tweak the arms just enough to loosen them up. wipers are suppose to be loose enough to "flop over" when the arms change direction. if they skip/hop then most times it's due to the wiper NOT flopping over and being forced across the glass with it's leading edge trying to scrap the water off as opposed to wiping the water off.
this video explains it a little better than I can ... hope this helps