Here's a trick that I've been using for a while that may or may not work for anyone else but it's been a blessing for me. I sew everything right on to the paper. I cut out whatever pattern I'm using, fold the spandex over and pin the paper down tight. Then I sew along the pattern line either by hand or machine. Once I backstitch and tighten it up I peel the paper off and turn it. This gives it body and reduces all of the floppiness. I think someone else mentioned it, but use a blunt needle. Sharp ones tend to get caught on the spandex and snap the thread.
Even using the above I still mess up 2 out of 3 times when I sew. I waste so much spandex, but to get a suit or cape right I've got to go through maybe a third of a yard to do it. I'm still a very basic sewing guy making gingerbread suits. I've got a ways to go improving my style, making patterns and just using the machine with a steadier hand and a gentler foot pedal.