This mixed-method study examines the effectiveness of teaching Google search techniques (GSTs) to Korean EFL college students in an intermediate-level academic English writing course. 18 students participated in a 4-day GST workshop consisting of an overview session of the web as corpus and Google as a concordancer, and three training sessions targeting the use of quotation marks ("") and a wildcard (*). Each session contained a pre-test, a 30-minute training, and a post-test, and each training session focused on one of the three key writing points: articles, collocations, and paraphrasing. Two questionnaires for demographic information and GST learning experiences were conducted. The results showed a statistically significant effect for the overall gain score. In particular, participants' use of articles greatly improved after the training--in contrast to their use of collocations and paraphrasing. Lack of grammar and vocabulary knowledge seemed to hinder their data-driven learning, especially for collocation use and paraphrasing. The questionnaire data showed that all students found the GSTs beneficial, mostly because they were easy to use for confirmation and correction. Overall, both quantitative and qualitative data suggest that teachers' meticulous guidance and vigilant individualized feedback are necessary to facilitate L2 self-directed Google-informed writing.