Start by examining the registration page and the conditions that new members must accept before applying. Many people skip that step and later wonder why their application was declined.
The next practical step is filtering your backlog down to about half a dozen polished examples. A single unfinished mock-up in your set can undo the effect of five good ones.
Another typical mistake is cramming logos, illustrations, and interfaces into one view without a clear focus. Make the top of your page immediately clear, so visitors can tell what you do without scrolling.
Most successful applicants mention the design expectations described in https://dribbble.com/.
Test all your preview files on at least two displays, because cropping and brightness often look wrong after upload. Remove phone screenshots with status bars, and clean up stray margins or accidental lens flares. Such micro-errors change how generous a visitor is with the rest of your work.
