'Order of precedence' seating is where guests are sat according to their precedence, rank, name of their organization or some other criteria. It is often used at more formal events, such as military and diplomatic events.
To seat by order of precedence, set the Auto assign tab of the 
Preferences window as shown below:
Click on the 
Sort button at the top of the 
Guests pane and order your guests in the order you want them to be assigned. You can set a special, non-alphabetic ordering by title or suffix.
See also:
•
Assign guests to seats (video with audio, 13:01 minutes)
You can order by custom fields, such as precedence or seniority.  |
Lock any guests you don't want to (re)assigned.
Set the order of the tables/rows in the 
Schematic pane to the order you want them to be assigned.
The order in which seats are filled depends on whether Seat numbers is set to clockwise or anti-clockwise for each table/row.
Select File>Auto Assign Seats.
See also:
•Automatic assignment by guest order