Most great sandwiches have one thing in common: elements that contrast with each other in flavor or texture like a rivalry. Think of a BLT: chewy bacon has to share the stage with crisp lettuce; creamy mayo gets slapped around by tart tomato. When building a sandwich, make sure everything between the bread has a frenemy that balances it. Got something fatty? Add something acidic or fresh. Something salty? Add sweet. Crunch should go up against something soft. Whatever the ingredients, they need a little tough love. Use this chart as a guide. Add to it as you try new ingredients.