Are there lifestyle changes that really make getting placenta previa less likely?

No. The location of the developing placenta inside the uterus is a random fertilized ovum implantaion event. Placenta previa occurs when implantation occurs low in the uterus by the cervix and "overlaps" the cervical opening(canal) which is more common in women who have had previous children than those who have not.
No smoking. Previa: Placenta overlies the cervix/birth canal. Gr 1 means placenta is close, Gr 4 means it's directly overlying/blocking the baby's exit -- high chance of preterm labor & bleeding; you'd need a C/S at 36-37wks. More common in woman w/ hx of C/S & smoking. Not much you can do but wait. If dx'ed early, the uterus still grows/stretches and a placenta can migrate away even in 3rd tri. Follow w/ US.
Not really. It's really random. The best thing to do is to recognize it early and develop a birth plan with your doctor to avoid complications. Make sure there is no accreta which would lead to hysterectomy - a difficult surgery with a term pregnancy.