>>>In VFP 5.0 what is the best way to inforce unique values in a field? Should I put some code in the triggers? and what triggers.
>>>Thanks
>>
>>The straightforward way is to create primary/candidate tag on this field.
>
>How do I create this tag? Is it code in a trigger or rule?

Use Table Designer. You can do it in code too: INDEX ON ... TAG ... CANDIDATE