Which one in particular?
Local requirements sometimes vary depending on whether it's radar controlled or procedural. Best to check the ERSA.
Normal order is taxi first, then clearance, or you can make them both at the same time if you're comfortable enough with the amount of information you'll get back all at once.
If you're unfamiliar with the aerodrome, then request detailed taxi instrructions after landing and make sure that you have a clearance before crossing an active runway.
A