I always try to compliment people if I see they're taking a lot of pride in their work or something they're doing. I was at a conference where the staff each had a coffee/tea/sweets station to maintain. I noticed one woman cleaning and polishing and being super fastidious. I wanted to compliment her, but then I debated with myself if that would be patronizing somehow. Finally, I decided to tell her she had a very nice station, and she just beamed ear-to-ear in response.