anager.
...I remember when I first started waiting tables I had a customer who had put wastepaper (from sugar packets and creamer) on her plate so I assumed I could take that one away for her. Nope! She quickly stopped me from taking it, saying "I'm not finished with that!" Yes, the plate still had a small amount of food left on it, but who puts wastepaper directly ON the plate they're eating from?! I thought that was very odd, but it taught me to ASK the customer FIRST if they would like me to remove a plate that I thought they were finished with. Of course unless they were stacked and put to the edge of the table, then I just automatically took them away...
One thing that annoys me when we go out to eat is when I get a salad with my meal sometimes I'm not finished with it when the meal comes, and I push my salad plate away a bit so they can put the plate down and then they reach to take away my salad plate. No, please leave it as I might finish it when I'm done with my meal (I won't let food go cold while I finish my salad, so I just leave the salad plate to the side). It's especially annoying when they do that when a salad doesn't come with the meal and I've paid extra to get one.