In my Delicate Details workshop, I teach my students to dig deeper in their technique and we focus on everything from posture to small tweaks in movements that can change how you want to express the music. You practice your shimmies and chest lifts all day long but you're probably not polished in these 3 major areas. Assuming you practice with the correct posture and technique already (chest lifted, shoulders back, abs engaged, knees slightly bent, arms out & relaxed), here's what's most often overlooked:
1. Facial expressions
Have you ever seen a beautiful dancer with the perfect technique but looks like a deer caught in headlights? It happens more than you think (actually, it happens to all of us). This is where dancing in front of a mirror can really help: check out what your face is doing next time you're in class or drilling on your own. Give yourself a smile! Loosen up and make eye contact with yourself. Awkward, I know, but you want to welcome your audience, not ignore them. How you practice is how you perform so if you catch yourself looking down all the time or with a grimace on your face, you're probably doing that when you're performing.
2. Foot placement
This will vary slightly depending on how your body is built but when standing in a neutral position, you should have your weight placed equally and your feet should point towards the mirror or ever so slightly outwards with about a fist-width's of space in between (again, this depends on your body type). Your feet shouldn't point inward when you're doing any movement, especially when you're traveling. You could lose your balance and do damage to your knees and ankles, so really pay attention to what's going on down there. The most common time your feet may start to turn inward is when you're turning or doing some sort of combination of hip movements while traveling.
It's not enough to focus on your arms alone and expect your hands to look pretty. If your energy isn't carried on through your wrists and fingers, then your hands can looks all sorts of freaky when you dance and you're not even aware of it! Try the "Barbie hand": middle and ring finger together, pinky and pointer finger slightly upward, thumb tucked in but extended. If that didn't make any sense, just raid your closet for your old toys and dig up your old Barbie doll and you'll see what I mean.
So next time you're practicing, take a look in the mirror and see what's going on in these areas. You'll look more put together and after a while, you won't have to think about checking in with yourself to see if you're doing it correctly, it'll just come naturally!