I like to use staem-a-seam or steam-a-seam2 rather than wonder under. In the beginning, I used to trace the pattern on the fusible (paper) and cut exactly on the line before I ironed it on. Now I cut the pattern a little larger, iron it to the back side of the fabric and THEN cut on the line.
My favorite stitch to secure the applique is the blanket stitch and my machine does a good one.
Remember too that using fusible creates a mirror image of the design. Sometimes it's unimportant but when doing letters and numbers, flip the picture.