Destructive and irrecoverable actions should be guarded with a forcing function to ensure that a conscious choice is being made.
Monitor for accidental duplicate entries and guard against it.
The following dialog has an entire sentence explaining what the "OK" and "Cancel" buttons map to - and the mapping is also counter-intuitive - the user must click OK to cancel and cancel to continue. Labeling the default button with a clear "Save Document" would add clarity.
Free-form input fields provide flexibility of entry, but also increase the likelihood of bad input. Immediate client-side validation can increase input quality (example: uStream sign up form). Using more constrained input controls can also be helpful when applicable - but ensure that the constrained choices cover all possible scenarios. The second example from Microsoft Health Common User Interface shows that sometimes there are edge cases to be considered - constraining too tightly can cause situations where there is not an acceptable choice. Consider the possibility of allowing users to enter an "other" choice to give flexibility - standard choices can be adjusted over time as the other entries are reviewed.
Thanks for the feedback! It will help us improve your experience.