Below is a small paragraph which I copied from http://www.gentlebirth.org regarding preparation of Placenta for consumption
To cook, wash excess blood from the placenta. Place it in a steamer over water. Place with it fresh ginger slices, half a lemon and a hot pepper. Steam for 15 minutes, turn, and steam 15 more minutes until no juice comes out when pricked with a fork. (Steam over low heat, it has a tendency to boil over and that's a mess.) The membranes and cord may be cooked with the placenta. It is helpful to turn the placenta to "Schultze", i.e, wrapped inside the membrane when you cook it. It will shrink tremendously, and wrapped in the membranes makes it easy to deal with for the next step. After steaming, slice the placenta in 1/8" strips, similar to making jerky. Slice as thin as possible. Place the strips on a cookie sheet (over alum foil if you're squeamish) and place it in a oven on the lowest possible setting for several hours until completely brittle-dry. (Again like jerky) Using a food dehydrator is even better, but will take longer. Powder the strips in a coffee grinder, and encapsulate. I advise clients to take two capsules three times a day for two weeks postpartum. It can be kept indefinitely, but is best kept in a freezer long term (like any meat).