Decide your goal: stretch-and-pull (choose mozzarella/provolone) or browning-then-soften (choose halloumi).
Match the ratio from the table: start with 1:1, and drop to ¾:1 if your substitute is very salty (feta).
Prep for faster melting: shred harder cheeses and slice halloumi thin before heating.
Adjust in the moment—if the dish tastes too salty, add an unsalted base (neutral bread dough/neutral pasta) or reduce added salt.
Bake or heat until glossy and elastic; if it looks dry, cover briefly or add a teaspoon of water to the pan.