There is always great interest from people keen to find out about the military service of their forefathers.
Modern technology means it has never been easier to get started, but the route to finding out more depends very much on what you already know.
Name, date and place of birth are a near essential starting point, but knowing a regiment and service number will help greatly.
Here are five key resources to help you.
Imperial War Museum’s Lives of the First Word War
The Imperial War Museum has uploaded the basic details of 7,691,770 people who served in the Great War to its Lives of the First Word War website.
The free search engine allows you to key in a name and returns all of the men with that name, their rank, service number and regiment.
Users are encouraged to add their own information, photos and documentation so if someone has already got there first it can be a big help.
There are also community groups covering a whole range of topics from regiments and battles to the civilian careers of soldiers - for example, police officers and footballers.
The Ancestry website is one of the most popular online resources for researching family trees with more than 14 billion birth, marriage, death, census and military records.
The subscription service has a dedicated First World War section with access to war pension records, medal rolls, Commonwealth War Graves details and absent voter lists. There is a free 14 day trial.
See also findmypast.co.uk
British Newspaper Archive
For a subscription, the British Newspaper Archive provides online access to 26,124,769 pages from hundreds of newspapers dating back to the 1700s.
Trench Fever was Rampant on the Battlefront. Royal Irish Rifles at the Somme, July 1916
With a key word search, you can find articles relating to an individual, from death notices to reports of gallantry, plus interviews with soldiers on leave and awards of military honours.
If you are very lucky, you may also find a photograph, as they often printed the images of the heroic and the fallen.
Once you have identified your relative’s regiment it is also a great way of tracking their battalion’s action and you may even find a letter home written by them, as these were very popular during the early days of the conflict.
Once you have established which regiment your relative served in then it is worth contacting the appropriate regimental museum.
All have a treasure trove of photographs, records, books and other material on the history of that particular regiment. The standard of websites varies greatly but it is worth dropping them a line to see if they can help.
Some will invite you to make an appointment, some will charge for information while others are happy to help for free.
For the latter, a donation will always be welcome, as they are often run on limited resources and staffed by volunteers.
Commonwealth War Graves Commission
For those with relatives who were killed in action during the First World War, the Commonwealth War Graves Commission website is an invaluable resource.
The user friendly site is free and will help you find records of when and where a soldier was killed, his battalion and where his remains are interred.
Some records will also show a photograph of the headstone with details of any inscription and family names and a Grave Registration Report. It can also be a handy way for finding a soldier’s service number.