Separate the floss into individual strands and then recombine them. This is known as "stripping" the floss. There is less twisting and knotting, and the stitches lie flatter. To separate a thread from the others, hold onto the top end of the thread between your thumb and forefinger. Pull down on it with the other thumb and forefinger, taking all the other threads with you. It looks like a knot will form. Have faith. Everything comes out just fine.
Run each separated strand of floss over a damp sponge just before using it. This makes the floss lie much smoother and flatter. Some fibers, such as silk, should not be dampened.
If you know which direction you tend to twist the needle, give it a little bit of a twist the opposite direction after each stitch.
Try threading the needle with the "right" end of the floss.
Let the thread dangle every so often and untwist it.