Bleeding (usually heavy) maybe some cramping == == This bleeding may or may not be accompanied by crampy pains - a bit like period pains, or the bleeding can continue on for several days before the more serious pains kick in. Also be aware that this bleeding does not necessarily mean you will miscarry - I have always had bleeding in pregnancy and it has gone both ways.
If the bleeding does continue to the stage of being an 'inevitable' miscarriage, then expect quite strong pains and an increase in the amount of blood loss. Clots - sometimes quite large - can be lost. Occasionally you may see the baby, which sounds scary but isn't so bad when it comes to it.