Describe the intended change precisely
First identify what you want changed: a shorter hem, a closer waistband or an adjusted sleeve. “Make it fit better” leaves too many possibilities open. Try the item with the intended shoes and layers so the proposed position is based on the complete combination.
Mark the area only in a way that does not damage the fabric. During professional advice, the person assessing it can handle the pinning. Do not alter an item you have not definitely decided to keep; first establish your purchase or keep decision and the relevant conditions.
Look at construction rather than fabric quantity
A plain straight hem differs from an edge finished with lace, a zip or a complex pattern. Removing fabric may remove an important feature or require it to be reconstructed elsewhere. Even an apparently straightforward waistband change can involve pockets or lining.
On a jacket, shoulders and lapels are connected parts of the construction. Work there differs from a modest length adjustment to an uncomplicated hem. Ask about the specific intervention and likely result rather than assuming general adjustability. The visible difference in centimetres says little about the labour involved.
Consider effort alongside intended use
Obtain an assessment before deciding if the alteration is essential to the purchase. Include price, time and any limitations that will remain. An inexpensive garment does not automatically become a suitable choice when extensive work is added. Conversely, an existing frequently worn piece may justify a careful adjustment.
Ask what traces or design changes may remain visible. An old hem area, for example, may look different from untouched fabric; whether that matters should be assessed on the particular item. Do not assume an invisible result before its feasibility has been established.
Move in the garment again afterwards
After the alteration, try the garment under the same conditions. Sit, walk and check the affected area. The shorter length may be suitable while another movement still needs attention. A before-and-after comparison is more meaningful with the same shoes and layers.
Keep a brief note of the agreed result if several items are being altered together. That makes clear which length or width belongs to which garment. The work should answer a specific question about use rather than trying to replace an unsuitable design through an endless series of changes.
