When planning weddings or parties, I take the time to sit down and think about what things I have enjoyed at other weddings and events. You can even ask around to friends and family about their favorite weddings and what they liked and of course what they disliked.
After every party, I make a list of things that could have been improved, whether it is the design, layout or the organization. Of course with a wedding, you are hopefully only going to have one or a few of those to plan in your life. So you really do have to rely on other peoples opinions.
I think I have only been to maybe 4-5 weddings and that is including my own, that is not a lot of research material to go on. That is why I love this article by CandyJarChronicals.