First, understand what is will in legal term. Section 2 of the Will Act 1959 defines it as
“will” means a declaration intended to have legal effect of the intentions of a testator with respect to his property or other matters which he desires to be carried into effect after his death and includes a testament, a codicil and an appointment by will or by writing in the nature of a will in exercise of a power and also a disposition by will or testament of the guardianship, custody and tuition of any child.
Who to be witness
Gifts to an attesting witness or to wife or husband of attesting witness to be void
It means don't be a witness if you or your spouse is/are going to be the beneficiaries.
Going to marry?
Will to be revoked by marriage except in certain cases
It means, upon marriage, you need to write another Will else you have considered having NO WILL.
Validity of a Will?
No will made by any person under the age of majority shall be valid. (i.e. below age of 18)
No will shall be valid unless it is in writing and executed in manner hereinafter mentioned.