What is the best advice for buying an engagement ring?

Do not be sucked into spending several months salary on a ring. Don't let girlfriend talk you into going into debt just for a piece of jewelry. Be firm on your budget and what you can afford. Consider getting an wedding-engagement rings pair set than buy rings separately. Some guys even use family heirlooms such as grandmothers ring etc. I know Prince William and Harry had some of their mothers earring diamonds reset in wedding rings.