Wigs, whether natural or synthetic, are subject to the same curls, strays and general messiness that accompanies the hair on your head. This is especially true when the wig is new, where the time spent in the packaging could result in a haphazard array of hairs. Depending on the type of wig you use, the methods of flattening will slightly differ.
Wash the wig using a shampoo appropriate for the strand composition -- whether natural or synthetic.
Place the wig on a wig form. Spray detangler on the wig while it's still damp.
Brush the wig thoroughly, focusing on any tangled or raised spots.
Flatten tough spots on natural human hair wigs with a flat iron. Use quick strokes to prevent heat damage.
Reverse curls on a synthetic wig by looping the curl in the opposite direction around a ceramic brush. Steam the curls flat by holding a steamer in close proximity to the synthetic hair.
Spray the wig with hairspray to temporarily set the new shape.
Transport wigs and forms in a dedicated case to prevent smashing the wig out of shape.
Remember that brushes and hot styling tools can damage plastic wig caps over time.