Bought a camera from a thrift store or online? Bring it in for testing before taking it on that long-awaited trip!
You should enjoy your adventures for yourself and keep the moments in your memories, of course- but it always sucks to come back from a beautiful place only to find out you spent all that time shooting a dozen rolls of absolutely nothing.
For $10 I’ll run some BW film through your camera to diagnose for common issues such as light leaks, sticky shutters, focus issues, rough film gates, etc.