Consider the reliability of your sources and try to determine if the writer has a particular bias. Note how recent the information is. You would not want to write an essay on heart disease by citing a fourteenth-century medical treatise, although such a source would be pertinent to a discussion of the medieval world view. Try to determine how respected and well-received the source is, although you neednÍt necessarily reject sources which challenge traditional views.
Finally, trust your own reactions to your sources and add these to your notes. Of course, evaluating resources does not mean rejecting anything that contradicts your thesis. A strong essay will acknowledge and account for contradictory evidence.