Like ShockWave said, stabilizing the dream helps a lot. Another thing that helps is starting small. The things you listed that you were trying seem pretty advanced. Begin with putting your finger through your palm, or floating down when you jump. As those things become easier, try flying. Theoretically, if you absolutely, 100% believe you can do something in a dream, you will do it, but things like those listed above seem to come easier for most people. It did for me.
Good luck!