Hold those thread tails!
Added Jul 17, 2013
It is important you always have at least a 5 inch tail of both the top spool and bobbin thread. The reason is that when you begin to sew and as the machine needle raises up it pulls the thread tails into the mechanism of the machine under the feed dogs. If you have too short a tail, the threads get sucked under and caught into the mechanisms which cause the machine to lock up. So, the longer the tails the better.