This is a great stitch for edging appliqué pieces or just outlining motifs.
Bring your needle up through the fabric and thread a sequin, then seed beads (the number of beads depends on the size of your sequins). Go back down through the fabric a short distance diagonally along the line you're outlining.
Come back up next to your first sequin; if you have to place the new sequin first to make sure your spacing is correct, do so. Repeat until you've got a nice line!
You can also do this backwards (beads first, then sequin to finish); it's a personal preference which way to work.