Take your pick:
def my_view(request):
if request.method == 'POST':
print request.POST.get('my_field')
form = MyForm(request.POST)
print form['my_field'].value()
print form.data['my_field']
if form.is_valid():
print form.cleaned_data['my_field']
print form.instance.my_field
form.save()
print form.instance.id # now this one can access id/pk
Note: the field is accessed as soon as it's available.