One important but undervalued aspect of productive vocabulary is collocation--the ways in which words are combined with one another. To move from receptive to productive vocabulary, students need to learn a wide variety of ways that words collocate with each other. This paper describes the major types of collocations, typical collocational errors made by English-as-a- Second-Language (ESL) students in their learning process, and the teaching applications. Major topics covered include the following: vocabulary instruction and collocation; what is collocation; the arbitrary nature of collocation; pervasiveness of collocations; differences over collocation among linguists; a practical approach for classroom use; ESL students' errors that are related to collocation; how to teach collocations. The four attached appendices include a two week-long lessons of collocations, a 4-week vocabulary list, and a scoring sheet. (Contains 27 references.) (KFT)