Listen to your Doc. If it's early in your first trimester, usuallly not much different. In your late second or third trimester, listen to your doc. They'll prescribe rest, definitely to the hospital if you have any bleeding or cramping, and serial ultrasounds to see if the cervix has cleared. If it doesn't clear the cervix, a c-section is planned for delivery. Steroids may be given to help if you need early del.
Wait and watch. 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.
Avoid NSAIDs, sex. Placenta previa diagnosis comes with instructions: avoid all nsaids (aspirin, advil, motrin, Aleve - tylenol (acetaminophen) is ok), avoid all sexual intercourse, avoid tampons, douching or placing anything in the vagina, avoid exercise, avoid straining/constipation (colace, milk of magnesia great choices), avoid unecessary car rides, all travel and stay close to your maternity hospital at all times.