Here are some actual tips:
-Get a recording of your opera. You might even ask the Maestro or Artistic Director for a recommended recording - they're very different, really
-Have plenty of lozenges available all the time. Ricola offers free bulk lozenges to opera companies - visit
www.ricolausa.com-Have plenty of water available all the time, even if you are filling up pitchers at the drinking fountain and offering them on the tech table with plastic cups
-Try to keep dust and dirt out of the working spaces. Shake out costumes/prop blankets before the singer encounters them; mist with a spray bottle full or water (add a drop of eucalyptus oil for extra astringency) to settle dust in the air. If singers see that you pay attention to this, they'll love you forever.
-Pay special attention to the accompanist - this is an extremely difficult and often thankless job. (Accompanists tend to be very smart and funny, and usually have all the good dirt!)
-Train your ASMs well, and try to check in on them less. You have plenty to do already - let them set the props tables, and you shouldn't have to check them at all unless an ASM has a history of forgetfulness. Tell them over headset that you've called places, and make it their responsibility to tell you if they are missing someone - often, you might not have time to call attendance over com (and I find it annoying, anyway).
-Anticipate rehearsal skirts and practice props. Women usually wear some sort of gorgeous skirt onstage in opera, and they are also often tossed about or passionately embraced. Get them in a skirt early in rehearsals so that everyone can get used to her movement (and limitations).
-Start your WWW before rehearsals even begin. Opera is fairly straightforward, so you know when Tosca will enter - Puccini wrote it in the score. You'll have some unanswered questions, but you will be able to make excellent headway, keeping you ahead of the game.
-I ask chorus folks to wear nametags in the rehearsal space, and I write their names on index cards that are color-coded by voice type. Directors love this! They can group all the soprani together easily - keeping the Maestro happy too.
-Know your opera lingo: tutti, sitz, wandel, apprenti, repetiteur, toi toi, etc. These Italian/German/French potpourri are standard terms in this field.
-Ask in early rehearsals whether your principals want their entrances cued or not. Some prefer this and will look for a cue every time; others hate it and will ignore you at best, or get annoyed with the cue at worst. So just ask what they want. And keep an eye on them just in case they flake-out one night.
...hm, that's all I can brainstorm for now...!