This document summarizes a study that compared the effectiveness of three different approaches to tagging online resources: freestyle tagging, dictionary-based tagging, and a combined freestyle and dictionary approach. 78 undergraduate students tagged resources using Diigo over five weeks under one of the three conditions. The findings showed that dictionary-only tagging reduced redundancy and synonyms the most, while freestyle tagging resulted in the most single-use and irrelevant tags. The combined approach was most effective by allowing students to both use predefined tags and add their own. The implications are that students need guidance to learn effective tagging and that dictionaries can help structure the activity while allowing flexibility.