As with any lacework, the beads chosen must match the thread used (for weight and color considerations), for presentation, and the potential use for the lace. Tatting varies from a light, spiderweb-like consistency to a chunky, solid work depending on the thread used and the pattern design employed. Even the standard seed beads can be too large for the smaller tatting threads available (size 70 and smaller.) Certain sewing threads can easily be adapted for use in tatting. Mercerized quilting thread is stiffer than usual threads and can produce a crisp tatted piece that has the "body" to carry the seed beads. But the beads tend to look a little out of place on such a thin thread; from a traditional standpoint. Smaller seed beads typically used in embroidery are available and work wonderfully on small threads. When the threads used for the tatting get thicker, the type of suitable beads increases. Beads that are too large for a design or thread will have a tendency to sag or distort the shape of the lace. Rather than enhance the lace, it detracts from the beauty of the piece.
Besides using beads that are too large, using too many beads or using them in the wrong places can overwhelm tatted lace. The picots are instrumental in providing the "lacy" appearance to this type of work. Placing beads on too many picots can turn a beautiful piece of beaded tatting into a droll bit of glass and cotton knots. A good plan to follow is a one third / two thirds rule. Work a maximum of one third of the lace with beads and leave two thirds unembellished. Unless you are working a free-form piece, try to arrange your beads in a symmetric manner to achieve a balance and to match the regular nature of tatting. If you add beads to a free-form piece (a tatted work that is made to resemble a bit of nature such as a flower or leaf), then one doesn't have to balance the placement. A few beads used to mimic dew drops on a leaf or flower can produce a nice effect.
Finally, the ultimate use of the lace greatly determines the type, size and placement of the beads. Tatted earrings can support a surprising number of them. The weight of the beads helps contribute to the dangle. Beads used in tatted edgings can help the design keep a good line and definition as it hangs at the bottom of a piece of linen, but can cause the tatting to curl or collapse at the top and sides of the piece. Medallions are extremely versatile. As clothing or fabric accents, they can support many larger beads since the design will be stitched onto a backing material. The added support from the background helps distribute the weight of the beads. Medallions used as window accents will probably need stiffening with starch or similar to support the extra weight.