HOW TO RESEARCH A WAR MEMORIAL
After that, I should think the county record office would be the first port of call. That would give background on the village (if that is your interest); there might be publications of local relevance, and the staff could tell you what else might be available locally. I enjoyed looking through the register of Lydford school.
For my book on the Lydford war memorial, I spend a long time spooling through microfiches of the local paper, The Tavistock Gazette. It was a very laborious process although I found loads that was interesting, not necessarily because of a connection with the war memorial. Every so often I would come across a reference to one of the names on the memorial -- for example playing billiards or taking part in a church social. There were also occasional obits, as well as an account of the war memorial being unveiled. It was time-consuming but gave me a feel for both the period and the place, as well as all sorts of unexpected historical sidelights (for instance, an item from 1916 saying that cocaine was now illegal. Before, it had not been.)
There are a couple of good websites for family history -- i.e. ancestry.co.uk and findmypast.co.uk. I seem to remember that they give you a few months of trial period for free, although after that they charge. However they have some indispensable records. Ancestry in particular is linked to the National Archives at Kew, having digitised some of the records. The census records are key. They will help you place the men in the village.
In terms of researching their careers under arms, I would suggest going first to the National Archives at Kew. Their catalogue is online. You can look up the records of individual servicemen where they exist (some records were destroyed in the Blitz). Soldiers were entitled to various medals, depending on when and where they fought; the medal cards which list who was due what are available online. Silver war badges or medals were awarded to soldiers who were wounded.
The next step is to find if the battalion war diary exists for the relevant battalion. All battalions had to keep one but some of the records were destroyed along with the other records. I was generally lucky with mine. If the soldier wasn't away from the battalion (e.g. through illness, which will be recorded on his papers) you can tell what he must have been doing on any particular day. The deaths of officers are noted by name, other ranks are generally just given as numbers. The quality of the war diaries varies but they make fascinating reading.
The Imperial War Museum and National Army Museums are invaluable. The IWM in particular has a vast archive, of every conceivable kind of record – letters, diaries, official papers, photographs, voice recordings, film, memorabilia. It is digitising some of those for the First World War in time for the centenary I believe.
If you know when a soldier was with a battalion, you can find records from people who were, so to speak, standing beside him. They might take the form of diaries or letters -- sometimes quite brisk and businesslike, but others very vivid indeed.