The first thing you need is a working knowledge of embroidery machines, and an idea of how your drafted design is going to look embroidery size.
Your artwork is your jumping off point. A digitizer will scan this and then begin creating the design digitally. Create a design that you love; something with images that will endure, and draft it in as much detail as you can. Keep in mind to have the appropriate spacing.
The phrase “less is more” pertains to embroidery designs. Allow your digitizer to eliminate superfluous shapes and colors. Also use your imagination and try to envision the digitized design as stitches, in embroidered size.
When embroidering, any text or names should be the last thing you put in. A good knowledge of the different fabrics you might be using is essential. Textures and thickness will affect the perfection of your stitching. If you are going to be using different fabrics your settings should be for the unstable fabrics.
Experiment with your backings, keeping in mind that the more expensive ones may be the best. For caps, a medium weight tear away backing might be best, while satin jackets will require a heavier weight backing. Heavier backings are good for the more unstable fabrics. You need stability for the fabric. In general, cutaway backings are better than tear away backings. But try different ones and see what works for you.
Needles matter. Tight woven fabrics like terry cloth, corduroy, and denim will need sharper needles than, say, knit fabrics. Heavier fabrics would do well with titanium needles which are much stronger than ordinary needles, while needles that are Teflon coated glide through fabrics with ease.
Good embroidery design is technical to be sure, but it is also personal, and you should freely bring your own flare to your design. If you are going to do the digitizing yourself, be sure you have mastered the techniques involved before you begin to sew. One step at a time and your design is going to be exactly how you want it to be.