Cats were definitely more vocal when their owners left compared to strangers....Here is my little tips
If a cat seems shy or aggressive then I approach them slowly, not looking directly at them.
►Get down to the ground to make myself smaller so I am never towering over them.
►Put my hand next to the side of their face so they can smell if the like
►Sweep my hand along the side of their neck and down their back with medium pressure.
Basically trying to let them know that I am in control of the situation so they don’t need to be nervous, and that I am not threatening to them by being slow and concise in my movements. This usually works with most cats but not all.