what are some grounds for protesting a will

You can object to a will on the grounds that it was created as a result of undue influence.  That means that someone who is a beneficiary exerted influence on the testator (person whose will it is) to change the will or make them a beneficiary.  You can also challenge the will on the grounds that the tesator  lacked capacity to make a will.  You can also claim fraud, that the signature on the will was forged.