Millions of men served in the army. You need to do everything you can to make sure that you can spot your man from among others. If he has a common surname this is vital, for you could be looking at hundreds or even thousands of men with the same name. So what kind of information helps?

His full name. From family knowledge, a birth, marriage or death certificate. While it was not necessary for a man to enlist using his full name or provide any evidence of it, it obviously helps if you know it.

His regiment and/or number. If you do not know this, your life is going to be rather harder. It does not stop you - but it may be difficult to decide which man is Grandad from others of the same name.

His background. Where he came from, his date of birth and the name of his next of kin are all pieces of information that can help you pick out one man from others of the same name.

Where he served or what he did. Family stories of Grandad being at a particular place or having a particular role or being wounded can all help.

Useful clues can be gained before you really start from * photographs * discharge certificates or other documents * 1901 census information * medals (look for his regiment and number stamped on the rim) * local newspaper cuttings