If you don't have time to iron, don't own an iron or simply don't like ironing clothes, you can use alternative methods for most garments. The key is to use moisture and heat to relax the fibres of the fabric. You can also use strategies to prevent and minimise wrinkles in the first place. Rumpled clothing is not conducive to a professional or well-groomed appearance.
If your garment is clean but rumpled, put it in the dryer along with a clean, damp washcloth or hand towel. Choose a dark cloth to go with dark clothing; a light cloth could leave white fibres. Use medium heat unless your garment requires a cooler setting. You can also spritz the wrinkled area with a bit of water from a spray bottle until it is damp -- not wet. After five to ten minutes, the air inside the dryer will be humid enough to relax the fibres. Do not leave the garment unattended. When you remove the garment, smooth it out and wear it or hang it right away.
If you do not have access to a dryer, use a spray can of commercial wrinkle remover. Hang trousers by their cuffs, hang shirts normally (by the shoulder), and lay sweaters flat. Spray the garment until it is slightly damp, then smooth the fabric with your hand or a lint brush and pull it taut. If you do not have wrinkle remover, you can mix twenty ounces of distilled water with one teaspoon of liquid fabric softener in a spray bottle. Use a fine mist if possible.
If you are working on a specific area such as a wrinkled shirt collar or misaligned pant leg crease, spray the area until damp and use a hair dryer on the warm setting to dry it while you pull the fabric taut, crease it or otherwise direct it as you wish.
To prevent wrinkles from occurring in the first place, always take clothing out of the dryer as soon as it stops. Hang clothes immediately. Fold down shirt collars, fix cuffs and put everything in place before the fabric cools. Button and zip garments as necessary to prevent them from sliding off the hanger. In the closet, try to keep the hanging clothes from being pressed tightly together.
Beware using coloured fabric softener, even watered down, on light garments. It could leave a stain.