Finished my rodeo shirt last night and figured I'd pass along the stuff I wish someone had told me before my first attempt. If you're doing heavy embroidery on a western-style shirt, stitch out your design on scraps of the actual fabric first. Embroidery thread behaves totally differently on a dense black cotton than on the muslin everyone tests on, and my first go-round the gold thread vanished completly against the dark base. Cut your garment pieces before you embroider, not after. Embroidering flat panels is a thousand times easier than wrestling a finished shirt under the needle arm, and you avoid crushing the collar and cuffs. Just leave yourself big margins around each panel so the hoop doesn't stretch the edges wierd.
For the trim, skip store-bought piping if you can. Make your own from strips cut on the bias and it'll curve around the collar and cuffs without puckering. Press every seam as you go, boring but it's what makes the front band sit flat instead of waving.
Last thing, add an extra layer of fusible stabilizer behind any buttonholes in embroidered areas. Mine held up great thru a full day of arena dust and one very enthusiastic two-step.