The safe way to change a will is to have a new one drawn; however, a codicil may be effective.
A codicil is a separate document used to make minor changes. It must be signed with the same formality as the will itself. It is not necessary to have the same witnesses on the codicil and the original will; however, both sets of witnesses must prove the will.
Do not try to change your will by drawing lines through items, erasing, writing over or adding notations. This may destroy it as a legal document.