Lightly toast walnut pieces in a dry skillet for 3-4 minutes before adding to the salad to intensify their nutty flavor and create a crunchier texture that won't soften quickly.

Toss the baby greens with vinaigrette only moments before serving to prevent the delicate leaves from wilting and to keep the raspberries from releasing excess juice that dilutes the dressing.

Whisk the Dijon mustard with vinegar and maple syrup first, then slowly drizzle in the olive oil while whisking to create a smooth, cohesive emulsion that coats the greens evenly.

Add crumbled feta cheese as a final topping just before serving rather than mixing it in early, as the acidity of the vinegar can cause it to absorb excess moisture and become soggy.

Make the dressing and toast the walnuts up to 3 days ahead, but keep baby greens and fresh raspberries separate in the refrigerator until just before assembly to maintain peak freshness and texture.