There are three requirements for a will to be legal.
1. It must be in writing. Telling a friend, relative or even your solicitor what your intentions are is not enough.
2. You must sign it.
3. When you sign it, there must be at least two other people present to witness your signature.
In addition, you should date it, specify that previous wills (if any) are ‘revoked’ (cancelled), and name your executor(s).
Make sure you give sufficient information about particular possessions intended for particular individuals, to ensure that they can be identified. ‘To my niece, the picture she likes in the living room’, for instance, would be a problem if there are six pictures and two nieces.
You should give details of the beneficiaries, including the address of each of them, if possible.
Generally, your will should be clear on what will happen to a bequest if the beneficiary pre-deceases you. For example, whether it lapses, goes to their children (and in what proportions), or goes to someone else instead. When you leave a bequest to a class of people, such as ‘my grandchildren living at my death’, make it clear whether that includes unborn children, so pregnancies are covered.
And you should say where you want the ‘residue’ (everything left over, once the specific bequests have been satisfied) to go.
Finally, it is desirable to leave details of your possessions (or at least, an indication of where such details can be found) with your will.