I agree with suern3 - Leah day has very helpful videos. I took her Building Blocks Quilt Along FMQ course (videos are free) and learned so much. One of the things she suggests is to leave the feed dogs up and set your stitch length to zero. She says leaving the feed dogs up helps with the tension. This is what I do now and have never had any more tension problems. A lady at my quilt guild was practicing FMQing and the back of her piece was a mess of "eyelashes" and tangled thread. I suggested putting her feed dogs back up and setting the stitch length to zero. She looked at me like I was crazy, but it solved her problem with no tension adjustment!