Examine the history of the two disciplines. Anthropology as a study of other cultures began formally in the late 18th century. Anthropology has usually been regarded as western civilizations studying other cultures that were less technologically advanced, which is why archeology is considered an anthropological discipline. Sociology became an academic discipline in the late 1800s and was more focused on studying the surrounding culture in which the researcher resides.
Consider the scope. Anthropology examines overall culture, which includes that culture's art, mythology and history. Sociology is more concerned about specific behavior, what causes it and the interactions that result from it.
Look at the study methods. Anthropology tends to use general case studies based on a more "big picture" viewpoint regarding culture, while sociology relies on quantitative studies that are specific to a particular group of people. A report that relies on a culture's history and utilizes numerous examples is more anthropological, while a study that focuses on a subset of people using surveys and data is more sociological.