I am also new in this field, so just provide some suggestions.
EBG generally can be implemented in following ways:
1) drilling a periodic pattern of holes in the substrate
2) etching a periodic pattern of circles in the ground plane
3) adding a periodic pattern of metallic pads which are shorted to the ground by vias
4) Uniplanar EBG
There is some rough relation between the geometrical paramters of the periodic pattern and the stopband frequency. Up to now, I decide the stopband by simulation.