expect to hear "songs."
If you're expecting the typical build & release of musical tension, you will be disappointed.
expect a deep and/or meaningful plot.
If it's a tragedy, there will be a betrayal/miscommunication and everyone ends up dead.
If it's a comedy, there will be a betrayal or two or more, a masquerade/cross-dresser/trickster and everyone ends up married.
expect good dialogue.
It's written to be shouted across a huge room and is often repetitive.
expect good acting.
You're here for the lungs, not the emotion.
expect character development.
The entire story can be related in three paragraphs.
appreciate the detailed/creative/bold sets and costumes
consider the history/context of the story and/or composer
appreciate the "conversational" style of the music (still working on this one myself)
appreciate the amazing power/range/skill of the singers
get dressed up - it's a fancy affair!
read the plot summary ahead of time so you don't have to read the subtitles to understand what's going on