If weak and over-flavoured can both taste muted, how do I tell the difference?

[Santa's Lil Helper]

Beginner question that has been bothering me. I keep reading that too little concentrate can taste weak, but too much can also flatten or mute a mix. If the end result is simply ‘not much flavour’, how do you know which mistake you made without mixing five new bottles? Do you dilute a small sample first, increase a second sample, or is there something in the taste that tells you which way to go? I’m trying to learn how to diagnose a bad mix instead of solving everything with another squirt of concentrate.