I'm not sure there's any right or wrong to using a seam ripper. The things you have to be careful for are definitely stretching or (BIG NO NO I HAVE DONE THIS TOO MANY TIMES) cut the fabric. I find that I go down the middle of the seam, but after seeing the idea of every 4th stitch or so to try that.
That doesn't necessarily mean that I am going to go sew a seam and then rip it out. I'm sure I'm going to have ample opportunities to use my seam ripper. They tend to multiply whenever I sew in a hurry.
M