Spend at least one and a half to two days and stay there.
Take the train from Sydney Central Station to Katoomba Station.
Buy the Blue Mountain Hop On Hop Off ticket just out side the train station. Buy the Scenic World ticket together.
Visit Scenic World first and then see the others.
Wear good shoes. There are a lot of walking path options through the woods that are really good.
Get the Blue Mountain Explorer brochure it has all the train time tables.
The Explorer ticket is also a guide book with suggested walking tours.
Most importantly get a good camera with lots of memory card space!