The Maths Trails teacher books and CD-ROMs introduce, develop and enhance mathematical problem-solving skills. 'Working Systematically' is part of a series of mathematics enrichment titles developed by the NRICH team at Cambridge University. This Teacher's Guide details 18 problem solving activities arranged in a trail progressing in difficulty. Each activity focusses on a specific skill or strategy that develops a particular aspect of problem solving. Full supporting notes for teachers include clear links to the curriculum, useful questions, prompts and hints for students and possible outcomes for each activity. Links to similar problems on the NRICH website are given and students are encouraged to post their solutions on the site.