Choose weaving sett
Sett is warp ends per inch or centimetre. A balanced plain weave and a warp-faced cloth need different densities.
Measure wraps first
Wrap yarn evenly without compressing it. Divide wraps by the measured ruler span. For a plain-weave sampling start, try around half the wraps per inch as ends per inch, then weave and finish a sample.
Adjust for the fabric
A more open sett leaves more space for weft and drape; a close sett favours warp coverage. Twill can pack differently from plain weave. Yarn compression, fibre and finishing change the result, so record actual finished width and pick density.