Some of it was already spelled out in the original trilogy for him all he had to do was join the dots together and add a few extra bits and not include things like Qui-Gonn and follow the O.T story.(he has left alot up to the viewers interpretion {of events etc} and left things unexplained)

I am sure I read somewhere, by the story of the O.T George said he was tied down to show Anakin as a child, which could have been avoided somehow, possibly

and the love scenes could have more off screen instead of onscreen which again I am sure I read he said he was tied down to that part of the story

Its too late now but we will never know, what might have been had Lucas colleberated more on the story, might it have come out different....