So that everyone has a good time, seat teens together, aunts and uncles together, etc. Try seating groups either by their relationship to you or by their ages.
As for the head table, the rule has changed so often that there isn’t one anymore. You and your better half can sit at a raised table with your wedding party below you. You can have your own table with a table on either side of you with your wedding party. You and your husband in the middle of a long table with men on one side and women on the other, or boy, girl, boy, girl. Parents and grandparents at the table or not, it’s up to you.
Stick to table numbers. Famous couples, places you’ve been, etc., are hard to see from across the room. If you do want to have something a little different add that below the number so that both the guests can find their table, and you get that extra touch to your wedding.
Reserved tables are all you need. You’re not obliged to have individualize seating cards for each guest.
It’s a good idea to have a “Reserved” card at the parents seats. They are the only ones that need preferred seating.