|I'll credit Georgene for inspiring me to share this tip. After sewing a seam, I immediately press the stitching line on each side of the fabric. This effectively "melts" the thread into the fabric, creating a ridgeless seamline. After pressing both sides, I then press the seam open, and it gives a very flat, very professional looking seam. This takes only slightly more time, but the results are really worth it.
Hope this helps