Long tables seating arrangement

Generally, you assign someone a table rather than an actual seat. So, unless your tables are ridicuously long or something, I'd just assing tables and let people choose where they want to sit.

I was thinking side by side for mine

Traditionally, you were supposed to seat couples together only until they reached their first wedding anniversary, and then seat them apart after that. The theory was that they could talk to each other any time, but that if seated separately, they could each meet new people who might become friends. (This was not just at weddings or at long tables; it was a general rule.)

I'm probably the only one here old enough to remember that rule. And no one at your wedding will. So, seat people however you like.

I am aiming for something more formal so would like to assign actual seats, plus the number of seats at each table would make it awkward for people to find their own seats (3 seats on either side of the table, and I don't want couples to have to split up).

Either way is proper. If you are seating side by side, you want to make sure you have an even amount of chairs on each side of the table so that a couple doesn't get split up. Seating them across from each other is also appropriate. It's your preference.

I'm bringing this back from the dead since I'm curious on everyones opinion on this and switched to my laptop so I can search instead of making a whole new thread.

If you did long tables, how did you go about it? Did you assign seats? Did you just assign tables? If you assigned tables did you assign couples next to each other or across?

Is it even okay to assign "seats"? I really didn't want to assign tables even but am considering doing it. Is assigning seats only really used for very formal weddings? Mine is going to be pretty casual and laid back, so would it seem weird?

Sorry for the bajillion questions. I'm home alone today since FH is at work and my mind is going crazy with wedding details.