How to always catch fish ?

I dont live in a city with coasts and beaches.

I've tried fishing for multiple days while travelling spending almost the whole time fishing with many baits but always failing even tho somtimes locals tell me it's a good place for fishing, i tried ports where i can clearly see sizable fish around but no success.

This time im travelling for a week, i've got limited time to fish, im wondering is there really a tip or method to almost catch something ?

Please need some help.