Include DATES or approximate dates of the birth/marriage/death as no-one can tell if you are looking for someone in the 1880's or 1960's!
Include a LOCATION: COUNTRY > Region/Province/State > City/Town - any thing that you might know. This couple could be from Australia or the Netherlands!
Include the names of any siblings/children etc that you might have.
The more information you provide, the more likely someone will be able to assist you.
An example below shows thousands of Mary and Robert Bains from all over the world, using the search engine at familysearch.org
and without further information it would be hard to narrow down to your ancestor.
79,515 results for >Name: mary bain, Event: Residence, Event Range: 1850-1940, Spouse Name: robert bain