Irons, to their credit, do spell things out for us (what with an aptly labeled "silk" setting for silk and all). So how come our cotton sheets are always creased, and our polyester tops have a weird sheen post-press? Here, a handy guide to ironing all your belongings like a boss.
Cotton: Iron on high heat while the cloth is still damp to the touch. Use the steam and spray buttons generously as needed.
Linen: Iron the garment inside out on high heat while the cloth is still damp to the touch. Use the steam and spray buttons generously/as needed.
Wool: Iron the garment inside out on medium-low heat, and use steam to dampen. (Iron onto a pressing cloth if desired, as an extra layer of caution.)
Silk: Iron the garment inside out on low heat, and just after a wash while still slightly damp—do not spray or steam. Again, use a pressing cloth if necessary.
Polyester: Iron the garment on medium-low heat while still damp. Spray as necessary, but avoid steaming. (Steam and/or high heat can leave a plastic-like shine.)
Nylon: Dry iron the garment on low heat. Don't steam, but spray if necessary.
Acrylic: Dry iron the garment inside out on low heat. Never steam, but spray if necessary.
Lace: Iron the garment while dry on low heat with a pressing cloth in between to protect. Do not steam or spray.
Velvet: Never iron, folks—this guy needs steaming.