OP here. I knew I could count on DCUM! Thanks so much for all the advice!

Hem the dress so it just brushes the top of your foot when you're wearing the right shoes. Also strike a couple of dancing poses during the hem fitting - if you bend your knees a lot (it depends on the dance style), you might need to go a bit shorter. Waltz shouldn't be an issue, swing might.

In addition to stairs, practice getting into and out of a chair, including scooting the chair forward to a table and back out.

It's stairs you should be worried about, OP!

The dance floor is flat. There is no way you or your dance partner can step on your hem if the hem is an inch shorter than the floor (while wearing your heels). You need to check that your gown is tailored to you, or fits your body well, so that there's no possibility of it sliding down on you while you dance. For peace of mind, you can have the dress 3 inches off the floor (with heels).

For stairs, going up: daintily gather some of the front of your dress in one hand while you go up the stairs, holding the rail or your partner's arm for stability.

For stairs, going down, if you don't want the hem to touch the steps (if they're dirty, or outdoors and it's raining): reach towards the back of your dress, gather some folds in your hand and move your hand to your side, effectively pushing the fabric to the front, where there's more room.

Above all: PRACTICE AT HOME. Dance a few steps, go up and down the stairs with gown and heels you'll be wearing that evening. You'll feel more secure and can stand tall on the night.

Enjoy!

hold it up and boogie

Tucked to hem it

I've also found that when I lift my arms up (when dancing with a partner) the dress goes up a bit and that helps. But definitely practice in it first to see that will work!

Have it tailored. A gown like that should be tailored anyway.

Definitely get it hemmed. Wear the shoes to wherever you get it hemmed and they can likely help you with the length. If it's a borrowed (like Rent the Runway or similar), fabric tape goes a long way to helping the dress be at the length you need.

Hoping DCUM fashionistas can help me here. I'm middle aged, going to my first black tie event next month and will be wearing a long gown. There will be a live band playing big band music so I'm expecting there will be some lively dancing. DH and I do a lot of social dancing but I've never done it in a long skirt. I don't want to have to hold it up in one hand - so how do I avoid stepping on my dress? Is it a matter of making sure the dress is hemmed a little higher? Is there a clip of some kind that could hold up the dress? Am I overthinking it? Thanks!