Being grammarian is truly an exercise in expanding your listening skills. Your basic responsibility is to comment on the use of English during the course of the meeting. Prepare a brief explanation of the duties of the grammarian for the benefit of the guests.
Upon being introduced as the grammarian –   Get a blank piece of paper and pen ready on which to make notes.
During the meeting — When introduced, briefly explain the role of the grammarian. Please limit your explanation to about 15 seconds.
Throughout the meeting —Throughout the meeting – Write down the names of all the Toastmaster members at the meeting who will have roles that require them to do some speaking (Toastmaster, members of the eyes and ears team, Word Master, Joke Master, speakers working on projects in the manuals, Table Topics Master, Table Topics speakers, speech evaluators, general evaluator).
Listen to them during the meeting and next to their names write down any awkward use or misuse of the language incomplete sentences, sentences that change direction in midstream, incorrect grammar, malapropisms, wrong pronunciation, etc.) and instances when they use the English language creatively.