Just came across a great list of 11 mistakes that intermediate Spanish learners make.
From the site:
A major distinction between an intermediate and advanced speaker of any language is the person’s ability to communicate as a native speaker would. An advanced speaker is able to express her thoughts in the same way the native speaker does, while an intermediate speaker does not have the same “feel” for the language and thus relies on sentence structures and cognates of their first language to communicate in the foreign one. This intermediate speaker is normally still understood, but there is something unnatural and awkward about the way their phrasing.
This ability to think and communicate as a native speaker would, is only learned after much practice and many hours of listening to native speakers until one way just sounds more natural than the others. However, to help with the process, I have compiled a list of a 11 common errors I often hear intermediate Spanish speakers make, who are still making the transition to advanced speaker.