The American Association of Notaries lists a set of common mistakes done during a notarization process.  However, most mistakes can be eliminated by using good sound practices.  Here is what they say are the top 5 most common mistakes:

• Missing Signatures: Always double and triple check that all needed signatures are complete
• Acknowledgment filled out incorrectly: Make sure the county, state, date and borrower’s name are all filled out and correct
• Font is shrunk down: American Association of Notaries claim having a dual tray printer eliminates this mistake. If there is no dual tray printer available, then legal paper is usually an acceptable alternative (but do confirm first)
• Notary stamp is illegible: Keep the Notary stamp inked up and carry a 2^nd bottle of ink to avoid complications
• Additional items were not collected: Verify all necessary items are present for the notarization such as copies of ID, credit card statements, powers of attorney and confirm method of payment accepted

For a more in-depth read, please check out American Association of Notaries!