On a different cruise line, we went directly to the dining room upon embarkation and checked out our table assignment. We had a party of 12 and they could only fit 10 there. They were able to add a small table on the end to accomodate all of us. I didn't like having 1 long table. I would have preferred 2 tables for 6. Our table was the first table when we walked in the dining room.
Teresa and Larry
#36-Carnival Splendor 9/16/12
7 night Mexican Riviera
#37-Allure of the Seas 11/11/12
7 night Eastern Caribbean
I have noticed that the higher status CandA and State room category generally gets better table locations. Depending how full, the ship will depend how they will be able to accomodate a change on board. When booking, get your TA to suggest you may prefer to be near the center location. Sitting near the entrance can be really isolated, however it is also quiet. Sometimes when full, they will open a side lounge (which is very isolated), this is very quiet.