The first time I wore a strapless dress properly, for a wedding where my usual long sleeve top would have looked like a mistake, I spent the whole reception doing that subtle hitch you see women do at every summer do, the little tug up and over, pretending it was a dance move. It is still the dress I reach for when I need something that photographs well and doesn't need a cardigan negotiated over it first.
It is not the dress for a day with real movement in it. Anything involving stairs, a car boot, a toddler who wants lifting, or standing near a buffet table for three hours talking with your hands, and you will be adjusting it more than enjoying it. I would not wear one to anything where my arms are going up and down all evening, reaching for things, because that is exactly the movement that walks the fabric down an inch at a time until you notice. On the colour front, I have had the most luck with anything structured in a solid, mid depth shade, navy, a good berry, a proper black, because strapless styles already pull focus to the shoulders and bust, and a busy print or a very pale colour only adds a second thing for the eye to worry about, usually right where the boning shows through. The difference between one that behaves and one that doesn't comes down to what is holding it up and not much else. A dress with proper boning sewn into the seams, a grippy silicone strip along the inside of the top edge, and enough structure that it stands away from your body slightly when you hold it up on the hanger, will stay put. One that relies purely on elastic and hope will not, and you will know within the first hour, usually the moment you sit down and feel it loosen across the back. Fit is everything here, more than with almost any other dress. You want it snug enough that you could, in theory, do a star jump without disaster, though I would not recommend testing that in public. Sit down in it before you decide. The two real fit problems are gaping at the centre front when you lean forward, and a top edge that digs in under the arms while still slipping at the back, which usually means you have gone up a size for comfort and lost the structure that was meant to be doing the holding.
Get the fit right and it is one of the few dresses that genuinely needs nothing underneath it to look finished, which for me is rare enough to notice every single time.