Most commonly used is an object/destination and verb structure and it sounds good. You could use either an object/destination or verb if it is still clear what the button does.
Examples
- "(Liste) Löschen" <> "Delete (List)"
- "Neue Liste (Hinzufügen)" <> "(Add) New List"
- "Im Browser (Öffnen)" <> "(Open) In Browser
- "Browser Öffnen" <> "Open Browser
- "(Datei) Speichern" <> "Save (File)"
- "(Datei) Speichern Unter" <> "Save (File) As"
Whether you should capitalize the whole label text or not, I do not know. I just try to be consistent in my programs.
Think of messages like "Click Here" or "Add More Info"
"Click Here"
simply shift it to
"Hier Klicken"
"Add More Info"
is a little different
"Details Hinzufügen" literally "Add Details"
"Infos hinzufügen" would be informal and "Informationen hinzufügen" seems to be long as a button label text at least in my experience.