You should choose the witnesses for your will carefully. They need to be legally able to witness the will. They should also be practical choices for the protection of your wishes in the future. They will watch you execute the will.
Your witness should be adults. They need to be over 18 years old.
They must be able to see you sign the will. Blind people can’t be witnesses.
They must not be beneficiaries under the will. If they are a beneficiary under the will (or married to a beneficiary) then all the gifts to that beneficiary will be void. This could lead to enormous stress and disappointment.
It is a good idea to use neighbours or colleagues. The witnesses can be related or married to each other.
A witness can be called to give evidence if the validity of your will is called into question after you die. It is therefore not a good idea to have witnesses who are significantly older than you, or who may move away and be uncontactable by the time you pass away.