While I’m complaining about finicky fabrics, chiffon is an annoyance as well--it rips and wrinkles at every opportunity. To counter rips, sew them up as soon as possible. Wrinkles are a bit trickier, since you can’t apply a lot of heat or steam to chiffon. It will melt under high heat, and it will distort out of shape when steamed.
Often people say to hang wrinkled chiffon dresses in the bathroom and take a long hot shower, but that never worked for me. My best luck in getting wrinkles out was either with an iron on the lowest setting, or to use my hair dryer on the wrinkle itself. I actually found the hair dryer most effective.
It also helps to let chiffon shirts hang outside of garment bags if at all possible, so they aren’t bunched up. Their own weight will help get rid of wrinkles that way. Just drape the bodice of the dress over a hanger or curtain rod. Try not to hang the dress from its elastic straps; lycra will stretch out under its own weight, and that gets worse when the lycra has seven layers of organza and 3000 rhinestones hanging off it.