You can build an AB stacking bilayer graphene from the graphite by increasing the lattice constant c of graphite. From this, the bilayer graphene FET can be built as the usual steps for a monolayer FET, which could be found in the tutorials.
As for what is the important, it is a quite general question and depends on the topic to be studied. It is difficult to give some specific answers. Strongly suggest you do some literature survey by yourself before doing practice scientific research.
