I always start with free jumping , starting the fences off small and building them up from there. This gives me the ability to see the horse jumping without a rider and to assess the horses ability. It also gives the horse a chance to figure out what to do with its legs without interference.
I always build a jump next to the outside of the arena with a sort of funnel - this makes it easier to guide the horse into it. ( see pic ) DSC00125.JPG
Once the horse has the idea that it has to go over the fence I then proceed with ridden work, starting with poles on the floor and gridwork before going onto small fences.
It is important not to overfence your horse.