Clay before wood

[Whittled Thumb]

What kind of clay should I use to sculpt a peice before I carve it?

[sbirkes]

Many professional and amature sculptors use Klean klay (google that to find suppliers and information). Klean Klay is a plasticine like, non air drying, sulfur free modeling clay. Quite often people think of "kids clay" when they think of plasticine type clays. (not Play Doh)
Being non air drying eliminates the working time limit you have to finish a piece. Your sculpt may need an armature to support itself or at least parts such as outstretched arms. It cleans up with water and is workable at room temperature.

There are lots of other options. There are lots of other reasons for using Klean Klay or not using it.