What form of identification can I use as proof of identity?

An officer may not take the acknowledgment of a written instrument unless the officer knows or has satisfactory evidence that the acknowledging person is the person who executed the instrument and is described in it. An officer may accept, as satisfactory evidence of the identity of an acknowledging person, only:

(1) the oath of a credible witness personally known to the officer;

(2) a current identification card or other document issued by the federal government or any state government that contains the photograph and signature of the acknowledging person (i.e.: Driver's License, State ID, Military ID, US Passport); or

(3) with respect to a deed or other instrument relating to a residential real estate transaction, a current passport issued by a foreign country.

Source: Texas Civil Practice and Remedies Code Chapter 121

May a notary complete a Form I-9, Employment Eligibility Verification

Texas law does not authorize notaries public to certify an I-9 Form, and the Form itself does not contain a notarial certificate. Therefore, notaries should not notarize an I-9 Form. However, it is permissible for a notary public who is an employee of a business to assist that business in filling out the Form - as long as that work is not performed in the employee's capacity as a notary public, and as long as the employee does not place their notary seal on the document.

Source: Texas Secretary of State

May a notary public determine which type of notarial certificate should be attached to a document?

No. A notary public who is not an attorney should only complete a notarial certificate which is already on the document, or type or attach a certificate of the maker's choosing. If a notary public were presented with a document that did not contain a certificate and decided which certificate to attach, that notary public would be "practicing law." Instead, the notary may allow the person for whom the notarization is performed to choose among the sample certificates provided to the notary with the notary’s commission. The notarial certificate must be in English.

Regardless of which notarial certificate is used and however it is worded, the notary public has a duty to make sure that the information contained in the notarial certificate is a true and accurate reflection of the notarization which the notary performs.

Source: Texas Secretary of State