1Start from the best original you have
A vector – an SVG, a PDF, an Illustrator file – beats every picture, because the shapes are already drawn and nothing has to be guessed at. If all you have is a picture, send the biggest one, cropped to the mark, on a plain or transparent background. Nothing downstream can put back detail that was never in the pixels.
2Decide the size before anything else
The size decides what can be sewn at all. A satin stitch holds from about 1.0 mm wide; below that it is a run stitch and reads as fuzz. So the thinnest line in your artwork, scaled to the width you want, is the whole question. At 20 mm a typical logo’s thinnest line is 0.32 mm and gone; at 60 mm it is 0.97 mm and clean.
3Let the shape choose the stitch
A band gets satin across it. A broad field gets rows. An emblem radiates from one centre. A rule that gives every shape the same fill is the difference between a mark that looks sewn and one that looks printed on – and it is the part a person is really being paid for.
4Look at it before you commit
Every stitch, at the size you asked for, on the screen. This is the step that gets skipped, and it is the only one that catches the closed-up lettering and the line that turned into fuzz. If it is not right on screen, it will not be right on fabric.