Look at the format
Cartes de Visite appeared in 1859, were most popular from 1860 to 1880, and declined in use from 1880 to 1889. They were usually made on thin card about 2½” x 4″.
Cabinet Cards were introduced in 1866, most popular from 1875 to 1900, and declined in use from 1901 to 1903. They were larger, 4¼” x 6½”.
If the photo is on a Postcard mount then it won’t date before 1902, when many photographers were producing studio portraits in this format.

Photographic Studio
The photo may show the photographer’s name and/or address which you might be able to check in local Trade Directories to pin down a date.
There might also be details of the card manufacturer and printer which could be checked in the same way.

Fashion
What the subject is wearing can always help. The following is adapted from an account by Jayne Shrimpton from her Findmypast Blog. (May 2011) (https://blog.findmypast.co.uk/family-photos-what-are-they-wearing-1406240689.html)
a) Women’s dress.
By the 1890s, naturally-shaped skirts had arrived, fitting closely over the hips, the main dating feature of this decade being the bodice or blouse sleeve. Women wore tailor-made suits, plain with little ornamentation (brooch at the neck), hair in a bun with no fringes. In 1890/91 a vertical puff appeared at the top of the sleeve and this gradually, about 1895, expanded in the upper arm to form the distinctive ‘leg-o’-mutton’ (gigot) sleeve. At its widest in 1895 and 1896, the puff gradually withdrew back up the arm during the later 1890s, resulting in a tight puffball shape or shoulder frill by the end of the decade.  Collars were high and with a ruffle or lace under the stiff outer. Sleeves became tighter by 1897 and frilled bodices came into fashion.
In the early 1900s wide sleeved blouses were still worn for a few years. Then came the hourglass silhouette – small waist and skirt that fitted the hips smoothly, flaring out towards a sweeping hemline. Blouses and bodices for formal wear could be very feminine: often decorated with tucks, ruches and lace panels, they were made full in front to emphasise the bust.
Plainer, shirt-like blouses were becoming usual for everyday wear, the ‘tailor made’ suit comprising fitted jacket and matching skirt providing a practical outfit for the modern woman of the new century.
During the 1910s a more natural line evolved. Slender one-piece or tunic-style layered dresses were worn for ‘best’ but for ordinary day wear a calf-length skirt and blouse were usual: after 1910 the high choker-like Edwardian neckline began to lower and by around 1914 an open blouse neckline with a collar was common.
Briefly, between around 1918 and 1920, a slightly high-waisted barrel-shape defined fashionable dress and during the early 1920s styles were typically rather straight and shapeless, dress and skirt hemlines still worn around mid-calf level.
In 1926 a dramatic change occurred and fashionable skirts rose to just below or on the knee, these shorter hemlines remaining in vogue until at least 1930 and offering a firm dating guide. In the early 1930s hems lengthened to the calf again, becoming fuller and more feminine, fluid, draped fabrics creating the soft, clinging styles that were fashionable for much of this decade.
b)Men’s dress
During the later 1870s and 1880s the male suit was tailored more narrowly, the jacket developing high, neat lapels and a handkerchief often worn in the breast pocket. The conservative, dignified frock coat was still favoured by the upper classes, but the stylish morning coat, with its distinctive sloping front edges, was popular with the business classes and for semi-formal wear, often worn with narrow pin-striped trousers.
By the turn of the century, a greater variety of male garments may possibly appear in photographs, including some items of sportswear and the casual blazer, popular for weekends and leisure activities. The most common outfit seen in studio photographs, however, is still the familiar three-piece lounge suit, which remained the regular respectable outfit for ordinary working men and did not change significantly for the first 20 years or so of the 20th century.
The typical lounge suit of the Edwardian era was slender or easy in cut, the lounge jacket made to around hip length and usually featuring neat lapels.
During the 1910s and 1920s, the jacket lapels were often longer, while trousers sometimes show a centre front crease and may have turn-ups. During this decade and for most of the 1920s, trousers often appear very short and decidedly narrow around the ankle, exposing either old-fashioned laced boots or the more modern, lower cut shoes.
Men’s styles of the 1930s are generally very easy to spot as the suit was cut much wider, the boxy lounge jacket – either single- or double-breasted – having broad padded shoulders and trousers being worn longer and looser in the leg.

Occasion
Most formal studio portraits record special occasions.
Sometimes dress clues appear in photos — white or coloured dresses with ornate hats or bridal veils were typically worn at weddings, while dull black clothes and black accessories were donned for mourning.

Other visual clues
Studio props may have been used and it may be possible to date them precisely.  Hairstyles, the composition of the subject(s), the setting and pose may also help.

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