An obit may give a marriage date, and less often a place of marriage, in which case you have a good lead. Place of birth of the first child is another lead. Census records, if you have them, are another lead.
Sometimes, people were rather mobile and the hunt is more complex. My wife and I were born in different, wide separated counties. We were married in a third county, and out children were born in yet another. My parents were married in a separate country, which was not the country where either was born.