All states have requirements for the execution of a valid will by a testator (the maker of the will), whether the will is prepared with an attorney's assistance or is a holographic will, which is handwritten and signed by the testator. Additionally, all states require that the testator had the mental capacity to make a will and was free from fraud, duress or undue influence. If you can prove to a court that any of the foregoing circumstances existed or that the will did not comply with the state's legal requirements, then you can break or contest the will.
Get a copy of the will from the estate representative or, if probate proceedings have been initiated, from the court. You will need to carefully review it to determine whether it can be contested.
Determine if the will was properly executed according to the laws of state where the testator lived. Although the formalities associated with executing a will are rather minimal, if they were not followed the will can be invalidated for that reason alone.
Examine the testator's signature on a printed will and on the entire document if it was written entirely by hand. Consult with a handwriting expert if the genuineness of the signature or handwriting is in doubt. A forged signature or writing would invalidate the will for fraud.
Investigate the medical condition of the testator around the time the will was executed. If the testator was suffering from a medical condition or was taking medications that would preclude him from have the mental capacity to make a will, this will be cause for invalidating the will.
Investigate the relationships of the testator and the beneficiaries in the will. A will can be voided if it was made under undue influence, such as when a trusted person influences the testator to make a will that benefits her.
File a caveat, objection or other appropriate notice with the court before probate proceedings begin in order to preclude the will from being probated until your objection is filed and heard by the court.
File your complaint or petition with the court stating your grounds for contesting the will. Be sure to include all valid grounds and indicate to the court your interest in the testator's estate. For example, how you may inherit property from the estate if the will is invalidated.