Although being a mobile notary is a very informal job, signing companies and borrowers seem to appreciate a well dressed signer. It doesn't take that much extra effort to look good, but it can get you more popularity and in many cases - a lot more work! Don't wear shorts, or ripped clothing. Try to wear casual business attire, or formal business attire. Slacks, button down shirt, and an optional tie and jacket are a good start for men. For ladies, any type of clothing suitable for the office works.
Make sure your hair looks good, and that you smell good too. Having good breath and a nice, but not overpowering purfume makes a good impression.