This paper describes student difficulties in first-year calculus classes and suggests some instructional strategies to address these difficulties. Participants in this study were 200 low socio-economic background freshmen majoring in business in Brazil. Results show that the main difficulties are related to lack of understanding of algebraic notation and graphs, lack of understanding of continuum, inability to interpret word problems, and confusion caused by the usual meaning of a word when its mathematical meaning is different. To overcome these difficulties, suggested initial strategies include explaining the idea of the coordinate plane and ordered pairs, helping students understand variables and graphing, teaching about mathematical modeling, and using appropriate textbooks in teaching the graphic aspect of concepts and algebraic notation. The paper includes several illustrated examples of problems together with teaching notes. (KHR)