• People are 3D. When tracing someone on fabric to make a pattern (for a t-tunic, or something), remember that people are NOT flat.
  
• A 3/4" seam allowance can become a happy, well adjusted french seam if you sew the first bit at 1/4", and the second at 1/2". This does not allow for turn of fabric, but a little smidge isn't going to hurt all that much.
  
• Whatever you do, don't try to stitch though steel boning. It won't work.
  
• For set-in sleeves, make sure the seams match up, like sides together. (I never remember to do this.)
  
• When doing a fitted waistband (this can be adapted to elastic, too), cut the waistband with one long side on the selvedge. Close the short edges, folding it unevenly, so the selvedge side is a little longer (maybe 1/4") than the raw edge, and leave it inside-out. (Or turn it; however this makes more sense to you is best.) Pin the raw edges of the waistband and skirt (or pants or whatever) together, and stitch. Turn the waistband right side out, and make sure the selvedge covers the stitching line, as well as the raw bits. Pin it in place, flip the item over, and 'stitch in the ditch.'
  
• Plastic tablecloths (the kind you can get at the dollar store) are really good for drafting or copying patterns.