• RSVP and not show up

-you should RSVP. RSVPs are important because they help the bride’s family plan for the correct number of guests. If there is an issue with your RSVP, you should contact the couple.
• WEARING WHITE!!
-White is a color reserved for the bride and flower girls. If you wear white, it is major fashion faux pas and insult to the bride.Consider wearing neutrals and solids—do not wear white, cream, or a pattern with a lot of white.
• Wearing red

-Red is also considered a fashion faux pas. The color red is bold and represents passion. Wearing red is typically an insult to the bride and indicates passion for the groom.
•Be on your phone.
-The bride and groom put in significant effort to ensure every detail is perfect, and they pay a lot of money for professional photography and videography. Put the phone down and enjoy!
•Interrupting a special moment
-Some guest may need to leave early, but you must consider the timing! For example, do not interrupt a special moment, like cake cutting, to say goodbye.
•Not Dancing

-The couple want to enjoy a fun evening. Join in and dance!
•Complaining
-This day is about the special couple. Each and every detail was carefully crafted to capture their love. So, put a smile on your face!

https://emilypost.com/advice/wedding-etiquette