For field label text, use a short, catch-all description (1-3 words) of the information that a user needs to provide. Field label text that gets too long can be overwhelming and distracting, especially in complex interactions and long forms. Supplementary information or requirements about what to input can be shown in help text below the field, or in a tooltip.
Use verbs like "enter," "add," or "input" in a field label sparingly
Field labels generally communicate what a user should input, rather than direct them as to how to do it. The component design of fields and other inputs already implies that a user needs to enter, add, or input information in order to move forward with a task or workflow.
If the interaction may be new or unfamiliar it can be helpful to guide a user with action prompts using these verbs, but for more common patterns (such as forms), this can get redundant and clutter an interface.
Don't add a colon at the end of a field label
Don't add a colon (:) at the end of a field label to imply that the label text applies to the field it accompanies. The design of the component already communicates the relationship between the label and the input field.
Use sentence case
Following Adobe's UX writing style, field labels are written in sentence case unless they contain words that are branded terms.