I don't know your level of experience, so apologies if these are obvious...
If the ceiling is white, I would bounce the lights off of it. If it isn't, I would affix foamcore or a bounce card to it. If the light needs to be hard, use a shiny reflector.
If you absolutely must hang a fixture, either use a spreader, a counter-weighted boom, or a crossbar on C-stands.
p.s. - If your fixtures are small and lightweight enough and the ceiling is acoustic tile, you could also use a gaffer grip. But be sure you cover the area above the fixture with aluminum foil or the heat from the lamp may scorch it (learned the hard way).