Most people ruin their deload by doing one of these:
Adding extra cardio. You feel guilty about lifting less, so you add long runs or HIIT sessions. This defeats the entire purpose. Your body needs less stress, not different stress.
Cutting calories. Some people think a lighter training week means less food. Wrong. Your body is actively repairing during a deload. Keep protein at 1.6-2.2g per kg bodyweight. Keep calories at maintenance.
Training to failure on lighter weight. Lighter weight does not mean max effort with fewer plates. Keep intensity low. Every set should feel easy.
Trying new exercises. A deload is not the time to experiment. Novel movements create new soreness and stress. Stick to what you know.
Dropping protein. Muscle protein synthesis is still active during a deload. Protein intake should stay the same or even increase slightly.