If you don't already practice pilates in general that would be a great step. My dance teachers always gave me the same correction. I have pretty bad lordosis (AKA a "sway back") and always had teachers constantly telling me to "tuck my pelvis".
Practicing pilates and working with imprint/neutral spine and being concious of the difference has helped me to be more aware of my body and my pelvic placement.

I would think about lengthening your lower back, and using your belly muscles. And as Pasdekat said, Pilates is absolutely wonderful (if not vital) for that! But yes, belly belly belly! Those are the muscles that lift your pubic bone which in turn tilt your pelvis (aka tuck). Hope that helps!

-Amy-Jo