Use a finer needle (11 or 12) and thinner thread. I also use bottom line in my bobbin so there is not so much buildup on the back of the piece, but that is a personal preference. Many people like to use the same top & bottom thread, do some samples so you can figure out what works for you. Use a stabilizer as that helps to keep everything nice and flat. I do run my machine a bit slower to keep all the stitches consistent. Satin stitch, blanket stitch, straight stitch (raw edge), blind hem stitch are a few that are good to use. I make a sample of what will be stitched out on a piece, mark my machine settings right on the fabric and keep for a reference.
Brenda