Wrinkles in backdrop

Try to solve it in this order:

1. Hang (usually overnite or longer) 
2. Stretch 
3. Spritz (amazing what a little spray of water will do) 
4. Light flat (Try moving the subject forward from the BD (4') and evenly illuminate it.)
5. Steam 
6. Photoshop

Other idea:

• Throwing the backdrop into the dryer, on low heat, with a small, damp towel or dishrag (to add some moisture into the dryer) and running it for ten minutes can help get the wrinkles out if you don’t have a steamer.
• The trick is to take it out of the dryer the moment it is done with the cool down (before it stops spinning and sits at the bottom of the dryer getting new wrinkles) and hang it up.

• Hang your background and apply misted water where you want to remove wrinkles. Wait 5 - 10 minutes and set something else up while it dries. Or, just mist it and take a hair dryer to it and watch those wrinkles disappear.

• One solution is to light the background separately. This works best with lighter color muslins, especially white. I use 2 mono lights aimed at the muslin from behind and slightly out of frame of the subject. If it's just a head shot, you can get away with one mono light aimed at the background from directly behind the subject. 
• The trick is to get more light on the muslin than you do on the subject. If you use adjustable light sources, set the ones aimed at the background at full and the ones on your subject to half, then meter for the subject. If you use non adjustable light sources, set the lights close to your background and set the subject lights further away from the subject and meter for the subject.
• This effectively washes out the background to a pure white with no wrinkles. If you still have a few visible wrinkles here and there they are much easier to retouch in post processing than when the background is lit the same intensity as the subject.

• Go from behind and gather one or more pinches about the size of a golf ball and twist a rubberband around them. It makes a sweeping drape effect that hides wrinkles. Of course this only works with solids.