first port of call

noun2

1. •
   The first port that a vessel calls in at after the start of a voyage

   • After leaving from Southampton, our first port of call will be Gibraltar.
2. •
   The first place to go to start a process.

   • When you move to a new country, your first port of call is often the local police.
   • To find the meaning of a word, your first port of call should be a decent dictionary.