What order do you have the processional?
In the processional, the bride will always go last, so you will use that thinking when ordering the parents and grandparents.
The bridesmaids can be organized in whatever manner you would like with the maid/matron of honor entering just before the bride (or the flower girl and ring bearer).
The groomsmen will enter in different ways. They can escort the bridesmaids or they can follow behind the groom. If they escort the bridesmaids, they will be ordered with the best man being last. When they follow the groom, the best man will be directly behind the groom.
Also know that it is tradition that the grandmothers and mothers be escorted by the ushers.
Traditional order of processional:
Groom’s paternal grandparents
Groom’s maternal grandparents
Bride’s paternal grandparents
Bride’s maternal grandparents
Maid/Matron of Honor
Bride and her father