Taken from Annie's Attic
The secret to using beads, is to experiment and have the right size needle. Nothing is as frustrating as trying to work with a needle that has too large an eye and won't pass through the bead (no matter how hard you push). Do yourself a favor, and get a good beading needle. Be creative, there are as many ways to combine your bead and floss colors as there are stitchers.
You can either match the floss color to the ground fabric, so the color of the bead is undiluted and shines like a jewel, or you can match the bead and floss colors to emphasize the depth of color in the bead itself. On some designs where the color palette of your stitches and beads is widely varied, you may want to attach beads with clear monofilament to cut down on distracting floss colors which may show through and around the beads. Or, what about using a clear bead, and creating your own colors by attaching it with a vibrant colored thread?
Size matters in matching beads to fabric, too small and you won't see the beads. Too big, and they will overwhelm the design. A good match of bead and fabric would be a bead the same size as a single stitch. The exception of course, is a larger bead such as a bugle or a pebble bead.
When it comes to putting them on, complete your Cross-Stitches and decorative stitches first, this will give you a good base on the back to anchor to. For attaching beads, I generally use the same amount of floss threads as I would for Backstitching. Anchor your floss end firmly, you'll use a good amount of tension because you want your beads to stand up like soldiers at attention. Attach your beads with either a Half Cross-Stitch, or the bottom leg of your Cross-Stitch, that way they will be angled the same direction as all your top stitches.
If you are attaching beads in a row, you should refer to the Bead Attachment Illustration below.
If you are attaching a single bead out away from your stitching, you might want to offer it a little bit of extra support. When using one strand floss, make the bead secure with your initial Half Cross-Stitch, and then complete the Cross-Stitch traveling through the bead a second time.
When using two strands of floss, first make the bead secure with your Half Cross-Stitch, and then finish the stitch without traveling through the bead a second time allowing your threads to lay on either side of the bead.
Just remember what I said in the beginning of this article, be creative and experiment! Adding beads can make your stitching fun and more beautiful than you can imagine.