Check the untreated cloth
Look for an even weave, loose edges, stains, folds and visible stretch. Measure a small square so later shrinkage is easy to compare.
Run the intended needle and thread through a corner. Notice drag, hole size and whether the surface recovers after the stitch is removed.
Test the preparation
If you will mark, transfer or pre-wash the cloth, try each step on a spare section first. Some marks spread, disappear too early or remain after the planned wash.
Record the water temperature, detergent and drying method. A repeatable test gives you more useful information than a vague rinse that cannot be repeated.
Stitch and handle a sample
Make a few rows at the intended spacing, then fold, flex and lightly rub the sample. The cloth should support the stitch field without becoming unexpectedly stiff or distorted.
Keep the sample with the product label. It becomes a reference for colour, shrinkage, needle choice and whether the fabric suits a larger or more heavily used object.