One thing I did for quilting a diamond grid was to use wide blue painter's tape. Tape a piece diagonally across quilt, then stitch down the edge. Keep moving the tape, and lining it up evenly. Since it is painter's tape, it does not leave any residue on your quilt top. You will have to change the tape piece once in awhile. Quilting a long straight line like that helps you get the 'feel' of handling the quilt top and adjusting your machine speed.