When you approach this pose with the blind goal of reaching your toes, you need to take a moment to reevaluate. The poses are meant to create space in the body. Approach standing forward fold with the goal of lengthening both the front and back sides of your body, and gravity will naturally facilitate the opening and release required to bring you closer to your toes.
From standing, bring your feet together so the bases of your big toes are touching. Ground your heels firmly into the floor. Take a slight bend in your knees. Bring your hands to your hips, draw your low belly in toward your spine to protect your low back. Then, hinge from the hips with a straight spine as you fold forward.
After the spine has released, if mobility allows, extend your legs to produce an even lengthening across the entire back line of the body. This pose creates a passive lengthening of your spine, hamstrings, piriformis, and glutes. Release your knees, find some softeness in your hip joints, and allow the spine to continue releasing. Let your head hang from the root of your neck, between your shoulder blades. Continue to ground your heels into the floor, lift your sit bones toward the ceiling.
Inhale, lift and lengthen the front of your torso just slightly. As you exhale, release more fully into the bend. Oscillate your torso with your breath, synchronizing your exhales with downward movement.
If you have tightness in the backs of your legs, don’t pull yourself down or force yourself into the pose. You’ll end up using your hip flexors, which will wind up causing tightness and congestion in the fronts of your hip joints.
Want to check out another pose? Here’s downward facing dog (adho mukha svanasana)