What can make a $300 suit look like a million bucks and a $5,000 look like garbage? The fit. It doesn't matter if your suit is wool, cotton or linen, the fit is always the most important thing about how a suit looks. Here's how to get the right one (and how much you should expect to pay for it).
Too big and they'll slope, too snug and they'll wrinkle and bunch. The jacket's shoulder should hug your body's shoulder. When buying suits, try going down a size to ensure a snug fit—you don't want to have this part altered.
You should just be able to slip your hand under your jacket while it's buttoned. Any more room (say, a fist's worth) and your jacket is too loose. Have the sides taken in. The nipped waist will broaden your shoulders and lengthen your torso—it should cost $30 to $40 at your tailor.
Your sleeve should stop just above the joint of your wrist, enabling you to flash a quarter-inch of cuff. And if you want your suit to fit like a magazine or catalog model, then you'll want to have the sleeves taken in to proportionally fit your arms—a tailor will likely charge you from $15 to $20 per sleeve.
If you want a contemporary look to your suit, you want flat-front pants hemmed with very little break, allowing you to flash a bit of ankle. (Sid Mashburn will tell you no break is needed.) You may need to have the legs narrowed slightly as well—it'll run you anywhere from $30 to $50 for the both alterations.