Floaty skirts certainly have their place in a stylish woman's wardrobe. Some more formal occasions, however, call for skirts with a bit more stiffness. A skirt with some structure can be flattering, especially around the mid-section. For an easy but temporary way to stiffen a skirt, use the spray starch method. For a permanent solution, a more-involved interfacing technique is more appropriate.
Spray Starch Method
Set your iron to an appropriate temperature for the fabric of the skirt. Turn on the steam setting, if the iron has one.
Turn the skirt inside out and arrange it on the ironing board, ready to press. Shake the spray starch bottle and spray a fine mist over the flat surface of the skirt. Don't be heavy-handed with the spray starch -- you are going to apply it lightly multiple times, which gives better results than a heavy spraying once or twice.
Press the fabric lightly, keeping the iron moving in smooth, straight lines along the grain of the fabric.
Move the skirt around the ironing board and repeat the spraying and pressing process until the whole skirt has been ironed. Feel the fabric to assess its stiffness. Repeat the process as many times as necessary to achieve the texture you want.
Fusible Interfacing Method
Turn the skirt inside out and examine its construction. Interfacing a skirt essentially means adhering a layer of stiffer material to the underside of the fabric. If the inside of the skirt has a smooth surface, like an A-line or pencil skirt, the process will be quite easy. A pleated or gathered skirt, however, is generally not suitable for interfacing. Decide whether you want to interface the entire skirt or just a portion.
Press the skirt inside out and press all of the seams open. Lay the skirt smoothly on a flat surface with the front side facing you. Lay a sheet of thin paper over the surface of the skirt and trace the outline from underneath the waistband, along the side seams and above the hemline. If you only want to interface part of the skirt, trace the outlines of that section. Repeat with the back of the skirt. Neaten the pencil lines. You might want to measure the skirt with a measuring tape and compare it to the paper pattern for accuracy. Cut out the paper patterns with scissors.
Unroll the fusible interfacing and spread it out smoothly on a flat surface. Pin the paper patterns to the interfacing and cut along the edges with scissors. Remove the pins and paper pattern.
Read the manufacturer's instructions for applying the interfacing to the skirt. Typically, you'll start by placing the interfacing, adhesive side down, on the wrong side of the skirt. The adhesive side will either be shiny or have tiny bumps all over it. Make sure the edges of the interfacing lie underneath the side seams, not over them.
Cover the interfacing with a press cloth, spray the press cloth with water until it's damp but not sodden, press the hot iron down on the surface and hold it there for 10 to 15 seconds. Don't move the iron around, just press down firmly at a 90-degree angle to the ironing board. Lift the iron and see if the press cloth is dry. If it's still damp, press the iron down again for a few more seconds.
Move the iron to an adjacent section of the cloth and repeat the process until you've pressed the entire area of the interfacing. Remove the press cloth, turn the skirt right side out and press the outside of the fabric.
Allow the fabric to cool, then examine the bond between the interfacing and the skirt's fabric. If the interfacing hasn't fully adhered to the fabric, iron it again with a press cloth.