There are a few tools that you'll want to get to do a neat job.
Using a groover, you emboss a groove 1/4" in from the edge, then you run a
ponce wheel along the groove, marking where the stitches will go. Using a block of end-grain softwood (like a cut-off from a 4X4), you punch holes where the wheel marked them with an awl, taking care to get them vertical; not at an angle.
Finally, using a needle and sailmaker's palm, start a few holes down from the end of a seam, stitch up, then backstitch back down and continue along the seam. Some people saddle-stitch with two needles (on each end of the thread), crossing each other at every hole; I just use one, and when I get to the end of a seam I back-stitch back to the beginning. Try to keep the tension on the stitches as uniform as humanly possible.