Listen to the opera before attending a performance.
Familiarize yourself with opera terms and format: an opera is made up of arias, which follow a pattern beginning with a tune, then another tune and a reprise of the first tune.
Read the libretto, or words, to an opera beforehand, if possible.
Find out the story line of the opera.
Use the music to cue you in to the drama.
Read about the composer, his influences and the historic period in which the opera is set.