Make sure the items in the list are in logical order (alphabetical, chronological, order of importance, etc.)
If no item is preselected, use something like “Select a vendor” or “Select an account” in ghost or hint text format. If you can’t gray out the text, you can use some kind of indicator, like parentheses.
If you need to, you can display ”None” as one of the options. It should have the same text formatting as the other options in the list.
Dropdowns are activated by clicking, not hovering.
Editorial
Present drop-down selections in sentence case (“Select an account”). If the drop-down list contains formal names, such as customer names or accounts, then those selections will appear in title case.
Don’t use “deselect.” Instead, use “clear.” The term “deselect” causes a problem for localization.
The list of options should be sorted in a consistent order (alphabetical, chronological, the most selected option, or by order of importance).
Don’t end text in a select with a period.
Keep option names as brief as possible. Aim for under 5 words.