Sara gave you a pretty good description on this one. We also this one in a few stages. First, they need a good down/stay. Then we lured with a treat to get them over on their side. Lots of belly rubs and a treat. Then a stay in this position until they get an "OK" release signal. We train the play dead or "side" with a hand signal (finger pointing out/then point finger up like after shooting a gun). Because it is on a hand signal, we can say anything silly and they will play dead. Hope that helps.
Molly and Murphy (tri), Katie (ruby), Casey (B/T),Spike the wonder pup (tri), Suzie (tri) and Penny (blen)