As said, you need a few things in order: accurate cutting, accurate lining the fabrics and precise sewing. I will bring in something new: reduce the size of the thread to the smallest you can deal with. Some machines can not work with very small threads, so use the thinnest you can. Another thing I always do is not to press my seams open. I press to set the seams after I sew them, but never press them open. I find that it distort the fabrics and I can not match anything after that. I just finger press.