Yes, I was caught by this where a student complained that I hadn't 
criticised the draft with the same rigour as I did the final piece of 
work.  After that I just put the following into my guidelines:

"You should see the Unit Tutor if you have questions about the content of 
a particular Unit or if you are unsure what is required for that unit's 
assessmen.  Unit tutors understand that students who have not studied for 
a long time will feel apprehensive about submitting their first 
assignments and may need some reassurance as to whether they are on the 
right lines.  Unit tutors will not mark your work twice but they will be 
happy to quickly read through a draft assignment and tell you if you have 
understood the question correctly and whether you need to make any changes 
in order to achieve a pass grade.  If you would like this reassurance, 
then please book an appointment with the tutor well in advance of the 
submission date.  At this very busy time of the year tutors will certainly 
not have the time to look at drafts at short notice."

And I would explain that I marked the final pieces of work very carefully 
and they were all second marked, etc. etc. and that I couldn't do that 
twice.  So I alwauys insisted that they couldn't email it to me but must 
actually come along with it and they I would quickly skim through it and 
pick up any gross problems.  This was not only to protect my workload, but 
also to make sure that they were not just passing over the responsibility 
for passing the assignment to me.  However, I have to say that recently I 
was a bit suspicious of a draft I was looking at with a student and said 
to her something along the lines that she should make absolutely sure she 
had written it herself and wasn't just using unattributed quotes - and she 
nodded sagely.  However, I obviously wasn't fierce enough because when she 
handed it in I then discovered lots of patch plagiarism.

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