One of the things I tell my parents at Open House is that students in my room earn their praise. When a student brings their paper up to turn it in with nothing but their name on it-they aren't going to get a "good job". I'm going to remind them what they were supposed to do. I tell them all the time that I want them to impress me and believe me, I let them know when they do.
That being said I do think there is something about everyone that can be praised and appreciated. I remember being a class when I was getting certified where they gave us a list of words we could use to praise kids: great job, super effort, you came to school today! :) That one still cracks me up. At least twice a year I mail home certificates like postcards. I fill them out with something I am proud of them for and mail them to their homes. I know kids don't get very much mail and will be excited to see this in their mailbox!