Toby's not a very vocal cat, so he has to come up with creative ways to let me know when his bowl is empty or he wants some canned food. I keep fruit on the counter top (apples, oranges, etc.), so he sits up there and knocks a piece of fruit onto the floor. If that doesn't get my attention, he'll do it again until I realize he wants to eat. If there's no fruit there, he'll use anything he can find (car keys, water bottles, cans of cat food) and use his paw to knock them off the counter. The other day, there wasn't anything but some empty ziplock baggies there, so he was prancing on them to make some lots of crinkling noise so I had to come see what he was doing.