High to low process

If your object was sculpted in another program then you'll need to export a copy of your high poly mesh from your sculpting program. They key is that you don't want to export the highest level of the sculpt. You want to export the lowest level possible while retaining the shape of your mesh.

Autodesk resources on the subject.
  1. Import the high(er) poly mesh into maya.
  2. Open up the graphite tools ribbon (Customize > Show UI > Show Ribbon).
  3. Under the "freeform" tab click the drop down arrow next to grid and select the higher poly mesh.
  4. Make and select a low poly mesh object.
  5. Change "offset" to about 0.1. This will bring the produced mesh slightly above the high poly so that we can see it.
  6. Click the "topology" button. You can now draw topology guidelines on the surface of your chosen object.
  7. Draw lines on the surface of your chosen object. When lines cross over each other and enclose a new quad a polygon should automatically be generated.
  8. Remember that when you leave "Topology" mode the topology guide lines will also disappear.

Alternately you can use the classic "Create Polygon" tool within the Edit Poly modifier. Alternately you can just use Mudbox.

  1. Import the high(er) poly mesh into max
  2. Right Click the main snaps toggle icon to bring up the snapping options window.
    • Deselect gid point snap.
    • Select face snap.
  3. Make a new mesh object and add an edit poly modifier to it via ""Modifiers > Mesh Editing > Edit Poly".
  4. Enter the polygon sub-selection mode.
  5. In the edit poly modifier of a new object select the "Create" tool.
    • Left click to add points.
    • Right click to finish a polygon.