Requirements for Being a Witness

Speaking of witnesses, what does it take to be a witness? Generally, a witness must be over the age of 18, and must know what is being signed. The witness also must (in NJ) be in the same room in sight of the person signing the will, and must personally witness their signature. Beyond those requirements, as long as the witness is not coerced into being there, and realizes what s/he is doing, the witness's signature will be valid.