Dresses of course always depend on the silhouette, but generally speaking a dress shouldn't fit too largely that you completely lose your shape, nor should it fit too tight and ride up when you walk.
The two-finger rule for pants
When trying to determine if you pants fit or not, a good rule of thumb is to follow the two-finger rule: your pants should comfortably fit two fingers in the waistband. Another sign of pants that may not fit is any puckering in the front or back.
Your shoulder seam on your jacket or blazer doesn't hit right at your shoulder
Getting a jacket sleeve altered can be tricky without a professional, luckily are experts at Stitch have years of experience and can ensure your jacket is altered perfectly for you. Not only should you check that your shoulder seam hits right at your shoulder, but you should also make sure that you can comfortably drive or reach out to give someone a hug, if not, you might need to think about returning your jacket or blazer for a different size.
Of course there are many other signs that your clothes may not fit and it is always best to see a professional to make sure you are always dressed your best.