def my_view(request):
    if request.method == 'POST':
        form = MyForm(request.POST)
        if form.is_valid():
            # ...
            return HttpResponseRedirect('/thanks/')
    else:
        form = MyForm()

        # Load initial form fields from GET parameters
        for key in request.GET:
            try:
                form.fields[key].initial = request.GET[key]
            except KeyError:
                # Ignore unexpected parameters
                pass

    return render_to_response('my_template.html', {'form': form})