Lordosis can be caused by weak abs, short or tight erector spinae, and tight hip flexors (illiopsoas, sartorius)- often accompanied by low back pain, and predisposes the person to disc rupture & hernia.
Focus on: stretching low back, strengthening abdominals, stretching hip flexors, and stretching hamstrings will help since the erector spinae are drawing the spine up, and weak abs & tight hip flexors are pulling hips forward into an anterior pelvic tilt.
Along w/ these, I've had good experience having the person perform training against a flat wall or mirror- keeping back flat- no curvature in low back. Muscular imbalances like lordosis can occur if the person sleeps in a fetal position or sits all day at work or drives a lot. At first, practicing good posture, they may feel awkward or say it hurts to stand correctly- only due to the fact they have experienced it wrong for so long & this feels right to them. I've asked them to be more aware of their posture throughout the day & correct it- no slumping shoulders/head forward, no low back folding in, no protruding abs.
Hope this helps.