Free BMD

Gone are the days of needing to make long searches through the bulky Birth, Marriage and Death index volumes at Somerset house, St. Catharine’s house, Middleton place, or fiches at the Family History Centre. You can now do it quickly on the internet. FreeBMD mostly covers pre 1900 entries, but the years it covers are growing rapidly.
FreeBMD has excellent search capabilities, you can specify searches in counties or registration districts and between specified date ranges

Searching FreeBMD for spouses
If you know the wife’s Christian name from a census you can search for a marriage using both the husband’s and wife’s names, often this will give you the wife’s maiden name without you needing to buy the marriage certificate.
Example
My wife has a large family named BIDWELL, 11 children born and living in Salisbury in the 1881 census (RG11/2071/23)
Arthur BIDWELL is 5 in 1881.

Arthur is living in Reading in the 1901 Census (RG13/1145/69/20)
         Arthur W. Bidwell Head/M/25 Traveller Wilts Salisbury
         Sybil do Wife/M/21 Gloucestershire Gloucester
         166 Castle Street, St. Mary , Reading, Berkshire, England
Search in Marriages for Arthur BIDWELL marrying Sybil (blank surname) in the date range 1893 to 1901 and you will get the following:
         Marriages Mar 1901 BIDWELL Arthur William Gloucester 6a 458
Before 1852, up to 4 marriages were entered on each page of the register. After that there are usually 2 per page. Each page of the register is identified by the District, Volume and Page. Click on the page number (458) to see all the people listed on the page and you will see:
        Marriages Mar 1901
        BIDWELL Arthur William Gloucester 6a 458
        NICHOLLS Beatrice Gertrude Gloucester 6a 458
        NICHOLLS Ernest Arthur Gloucester 6a 458
        ONLEY Sybil Gloucester 6a 458
So, I found Sybil’s maiden name is ONLEY without having to buy their marriage certificate.

Find when a person dies using Date of Birth in your search
The GRO index contains the age at death from 1st Jan 1866, if you know when a person was born then you can use that date to narrow down your such, this works well even for very common names.
To do this specify in the Age at Death field the Date of Birth as
EITHER @day/month/year OR use a range of dates: @day/month/year-day/month/year
Think of the @ sign as meaning born at this date.
The year must be 4 digits (e.g. 1875); either the day or the day/month can be omitted.
FreeBMD calculates the Date of Birth from the Age at Death and the quarter in which the death was registered. However, the Date of Birth derived from the Age at Death has a wide latitude, typically 18 months when a precise Date of Birth is supplied and 30 months when only the year is supplied.