1.) Cut out the fabric pieces.
Place the center front side of your corset pattern against the fold, and pin it to the fabric. If you have fabric weights, by all means use those instead.
Using a pencil, chalk, or some other non-permanent material, trace the outline of the pattern on the fabric. Cut around the pattern exactly, leaving no seam allowance between the edge of the pattern and where you cut. If you're making a corset with straps, leave a 1/2-inch of extra fabric at the ends of the straps only.
Do all of the above to the lining fabric you're using. When both pieces are cut out, lay them one on top of the other and compare; trim away any small differences between the two pieces.
2.) Baste the two layers together.
3.)Mark and sew the channels for the boning and busk
Sew along the marks to create channels for the boning. Straight pins are useful for insuring that both layers lie flat and even. Sew from the top of the corset to the waistline on all stitching, or from the waistline to the top--this avoids wrinkling and twisting the fabric. Test the first channel to see that it is indeed wide enough for the boning before doing the rest.
Turn the satin ribbon over and iron it (or not, depending on the nature of the corset fabric). Fold the satin ribbon over the edge of the fabric to the inside of the corset, and hem-stitch it by hand. Iron it again, to get some of the wrinkles out.
Take your remaining satin ribbon. Lay it wrong side up on the right side of the corset, with the edges even, starting at the center back along the top. Fold 1/2 an inch of the ribbon around the back center edge to the inside, and sew a seam 3/8 of an inch away from the edge .
When you reach the edge of the busk pocket, stop sewing. start sewing the ribbon down again on the other side of the busk pocket, and keep going until you get to the other back center. Leave 1/2 an inch of ribbon extra, fold it to the inside of the back center, and finish off the top.
If your corset has straps, sew the edging the same way around the armholes. Fold the ends of the ribbon back on top of the ribbon so that they won't show, and sew them down.
Slip the busk into place, and poke two holes in the fabric to match the holes in the busk. you can sew a buttonhole stitch around the holes, making sure not to sew the two layers together. Once the busk is in place, a ribbon will go through the holes in the lining and through the busk, and tie together in a bow on the front of the corset to keep the busk from sliding out of place.
Following the instructions for your grommets, insert and pound the grommets into place. If you've never put grommets into an outfit before, I highly recommend practising on a piece of cloth before you do the corset.
If you're not using grommets, cut a very small hole in the fabric, and sew a buttonhole stitch around it. You can also sew a buttonhole stitch around the metal grommets, to make your outfit look more period.
It is helpful to finish off the lace you're going to use to lace your corset with by rolling the ends small and either wrapping clear tape or thread tightly around them, or dipping them in wax. This makes it a LOT easier to lace with, and reduces curses and mumbles behind your back.
9.) Immediately rush to the nearest mirror