Ann,
If by machine: some machines have a setting that will cause the needle to sit in the same position for several stitches before going forward. If your machine does not have this feature, then start a few stitches ahead then back up to your starting position.
If my hand: take a few stitches in the same spot, then stitch forward.
The locking will keep the seam from pulling apart and is always done at a "Y" seam. Hope this helps. Suzanne