Beware of using "form" language in an affidavit to establish the affiant’s personal knowledge of the facts. A statement such as "I have personal knowledge of the facts in this affidavit," may not be adequate. And the danger of getting it wrong is that the affidavit is legally insufficient.
A good discussion of how far an affiant must go to establish personal knowledge is found in the Houston Fourteenth Court of Appeals‘ opinion in Valenzuela v. State & County Mutual Fire Insurance Co. The court of appeals held that a "mere recitation that the affidavit is based on personal knowledge is inadequate if the affidavit does not positively show a basis for the knowledge." "The affidavit must explain how the affiant has personal knowledge." (emphasis added).