Having the perfect fit is critical to your overall look! Good tailors are a must!

Dress Shirts:

In most cases, you should buy a dress shirt 1/2" larger in the neck than your actual skin measurement. This allows for shrinkage. You should have the optimum fit after about four washings.

Always err on the long side with your sleeves, also allowing for shrinkage.
If you have trouble getting any dress shirt to fit, try custom. If you are in the Dallas, we do great custom shirts.

Suits/Sport Coats:

Your coat should nicely cover the fly and the rear. To cuff your hand at the bottom of the coat may work for you, but it is a "wive's tale" to think that that is the standard. If your arms are exceptionally long, you would end up with a coat that is too long, by that rule. If your arms are very short, you could end up with a coat that is too short. Just cover the fly and the rear!

Your shoulders should be comfortable...not too tight, not too baggy. Based on the shoulder padding and the cut of the coat, you may wear a different size in different brands.

Your pant should fit well around the middle and the seat. If you wear your pants below your belly, inform your tailor about it so that your length is marked correctly.