I know that this topic has come up and been answered before but I will say my piece again.
You should not expect to sell every seat in your theater. If you do sell them all and everyone is happy then you should count yourself fortunate.
Now that I have said that, the next step is to figure out how many seats you think that you should actually expect to fill given that people are not going to be happy unless they all get to sit together. Next decide how many seats should be left when you start giving a low seats warning to the people buying tickets. Advise them to go directly to the theater and find their seats.(instead of wasting time in the lobby,restrooms, concessions, etc and then getting to the theater as the trailers are running and attempting to find seats in the dark.) You can sell out the theater and negotiate with people at the boxoffice in any way that you care to do so. In my experience they will tell you at the boxoffice that they will take anything but they will still expect to find seats together when they actually walk into the theater. They think that they can just sit on the floor or stand in the back as long as they are together. Unfortunately, we all know that that is not the case. When you get to the low seats warning advise your usher staff so that they can send someone in to assist with the seating. We generally go into the theater and make an announcement that the theater is going to sell out. We ask people to move to the center if possible and tell them that we will be asking them whether the seat next to them is unoccupied. (Typically no one moves when we ask them to move to the center but then I don't feel guilty about sending people to climb over them to get to the seats. When I have people ready to climb over them they often move to the center anyway.) Then we start finding the seats left and putting people into them. If anyone is unhappy they are told they can return to the boxoffice and either exchange their tickets for another movie or get their money back. Most of the time we have everyone in a seat and the theater is peacefully quiet before the first trailer is done. Sometimes it takes longer but that is not ideal as people are trying to enjoy the movie and they don't need the constant interruption from people standing/shifting/talking while trying to find a seat. Often, the tickets that are returned to the boxoffice can be resold because your efforts in getting people to go to the theater and helping people find seats gets the theater settled early enough so that you know where the seats are and which ones are together. We communicate this information to the boxoffice via radios so they can match them up with people that are still coming in. Remember that I said you should not expect to sell out all your seats. Do the best job that you can and let it go. Do not see $$$ for the empty seats that are left.
Now I will also tell you that size and arrangement of the seats does matter. I have to deal with 2 small theaters that sell out fairly often. They both have 11 seats in a row - one is 88, the other is 66. I also have two large 300+ seaters. They rarely sell out and are more difficult to seat people in by hand. However, I still use the same methods. I just know that I will have lots more empty seats in there proportionately than I do in the smaller houses when the show runs.
I notice that there is an element of psychology at work that controls how people react to tight seating situations. If they didn't really have a high committment level to that movie at that time, they are much more likely to return to the boxoffice for a refund. It is like they were looking for an excuse not to be there anyway. Then there are also people who just don't like crowds and don't want to be there even if they can find seats together. On the other hand, a ticket to a perceived hot show will make it easier for them to accept that they will not be sitting together and they are grateful just to be getting in. Star Wars isn't the only event type film with this psychology. Remember last November when we played Polar Express to respectable but not large audiences? Then, all of a sudden at Thanksgiving, Polar Express became the hot ticket. We sold it out in the 66 seat theater every show for days. People were more willing to take any seats and we had a higher occupancy rate. I will even confess that I once sold 1 more seat than we had in the theater because one lady wanted to see it so bad and she was going to sit her child on her lap. I just couldn't turn her down.
Our refund policy is the same at all times sellouts or not. We believe that our product is the showing of movies. If the customer has not seen the movie then they should get their money back without question. Our policy is always that the customer can come out up to 30 minutes past start time and get their money back. After 30 minutes we will give them a pass for most of the acceptable requests. We don't accept all requests for passes either - you can't come out 20 minutes before the end of the movie and demand passes because the PG-13 movie was too racy for your kids. You also can't demand a refund AND a pass because your show became a sellout and you chose not to take the seats that were available. (Yes, that really happened.)So we don't make everyone happy all of the time but we live life according to what we think is the right way something should be done. I believe that it is wrong to refuse refunds to people who are not happy with the seating arrangements and ask for a refund before the show has started/ within a reasonable time. You would be unnecessarily creating bad feelings and I can attest that there are already plenty of other opportunities to create bad feelings among your customers without looking like a greedy miser also. You just change your thinking that all seats should be sold and accept that they will not be.
Maybe I work in a different world from the rest of you guys but I have had people who have bought a ticket and returned 2 minutes later for a refund because they didn't like something about the theater - size, temperature, screen size, smell, lack of other people in the theater, whatever. Would you grant them a refund? If so, then why would you not refund tickets on a sold out show? The customer does not perceive that the situation is different. He doesn't like something that he encountered and he has changed his mind about seeing the show. You have only had the money for 2 minutes. It was never really yours. Give it back.