You an also order more than one appetizer, soup, main meal and dessert! when you order! You don't have to wait to see if you don't like it.
I too am pretty set in what I like and don't like, but I ordered at every meal an extra part of the meal because this is the chance for you to try something without having to have that be your only option (like restaurants on land). What I mean is I ordered 2 main courses, 2 appetizers, 2 desserts, etc. We shared them amongst our family so we could each try something new if wanted Please do not be nervous about doing it. We even went to breakfast for the first time at a MDR just to try it out, and I really wanted the omelet, but they had a plate that had cinnamon French toast that I really wanted to try. Not sure if I could order 2 things for breakfast and I asked the server... He said I could order 4 or more if I wanted... "it is your vacation". that was really sweet.
Others mentioned ordering Caesar salad not on menu... we often ordered a simple side salad with ranch dressing and they have no problem with that.
But agree with everyone, please let your servers know, they really do want to know because they can then accommodate your wishes. their survey at the end of the cruise is very important and are needed an "excellent" response, so give them a chance that they can earn it.
If you choose to use the APP on board then you can also look ahead at what is being served.
If for some reason you plan on skipping a meal at a MDR then please tell your servers as well. We saw some tables that they prepared for (drinks etc ) and no one showed up. Felt bad for the servers. that is time and food wasted.