Level of Experience: Beginner
Polymer clays need to be conditioned before sculpting. One good way to condition polymer clay is to first break off/cut off the amount of clay you want to use. Then roll it in your hands 30 seconds or so to warm the clay. Then begin to knead the clay (flatten, fold in half, and repeat). until the clay is soft and easier to work with. After conditioning your clay if it is still to firm or soft after conditioning you have a couple of options:
If to firm: Mix your polymer clay with Fimo Mix quick (if you are using fimo) or Sculpey Clay softner (If you are using Polyform clays).
If to soft: You can Leach your clay by placing it inbetween layers of paper. I use at least 10 sheets of white printer paper. 5 under neath the clay and 5 above the clay. I Then place something heavy on top of the whole stack. At least 24 hours later I remove the clay and check it. Usually by then it is ready to be sculpted with.