Choose crisp apples such as Honeycrisp, Pink Lady, Fuji, or Granny Smith because they hold their texture well. Toast the walnuts for a few minutes before adding them to bring out their natural flavor and crunch. Dress the salad just before serving to keep the spinach fresh and prevent it from becoming soggy. Start with a small amount of dressing and add more as needed to avoid overdressing the salad. Use fresh lemon juice for the brightest and most vibrant dressing flavor. Keep the feta in larger crumbled pieces for a creamy contrast with the crisp fruit and vegetables. Baby kale can be substituted for spinach, or you can use a mixture of baby spinach and mixed greens. Toasted pecans are an excellent substitute for walnuts and add a slightly sweeter, buttery flavor. Prepare the dressing, toast the walnuts, and slice the other ingredients ahead of time, but keep them refrigerated separately and dress the salad just before serving. Toss apple slices with a little fresh lemon juice after cutting to help slow browning. Goat cheese, blue cheese, or queso fresco can be substituted for feta. For a more filling meal, add grilled chicken, roasted chickpeas, quinoa, or another favorite protein. Serve alongside roasted chicken, turkey, grilled salmon, baked fish, warm soup, or crusty bread. This salad works especially well as part of a holiday meal or festive dinner spread.