The NASUWT have just sent me my ballot paper for strike action. As a supply teacher, if I do strike, do I just make myself unavailable for work that day? Do I tell them the truth about why I'm not available? Is making myself unavailable a big risk? Can I afford to pay for Christmas if I go on strike? So many questions. I want to join with my union, I agree with what they're saying and they've been good to me in the past. What to do?