My nan's and sister's dogs usually listen to me. They can hear it in my voice when I'm annoyed with them.
It's weird, I can read their body language really well and my nan just can't tell. I know when her dog wants a biscuit or tablet because she'll look to me when I say either of those words with a, "YES!!" look on her face. When she doesn't want food, she'll still look at me but without that intenseness.
Her tablet is squidged into this dog chew, BTW, so she doesn't really want the tablet as such.
She likes routine as well, so that helps.