1, Because it is ready to wear suit, it can not be as precise cut as customized suit, this should be kept in mind before you make any purchase, otherwise you may not be able to buy a good suit.
2, The 3 things to consider first for ready to wear suit is: shoulder width, chest and waist circumference and fit, all parts do not feel too tight and not too lax, after the placket buckle on the vertical can be more than 3 fingers can be the gap.
3, Such as the high demand for pants on the hip and thigh preferred pants, because the waist and pants length is relatively easy to modify some. If the requirement is not high, the preferred pants for the waistband is preferred.
4, After you purchased any suit, the sleeve length, blazer length, waist, pants length are all easily changeable with a local tailor. So don't worry about these numbers if there's some difference to your exact size.