New York, I'm sorry to hear that you failed CS. I also failed the CIS portion of CS and had to re-take it recently. I haven't gotten the score back yet, so I don't know if what I did helped.
For what it's worth, I reviewed the following books:
1. First Aid - good range of cases with differential dx and tests to order
2. Mark Swartz' The Ultimate Guide and Review for the USMLE Step 2 CS Exam - has cases and sample checklists of components of the physical exam and communication skills that are pertinent to each case. The checklists give a good idea of what SP's might be looking for.
3. Kaplan Step 2 CS - gives you examples of what to say when you're doing certain maneuvers and sample answers to those hard questions/difficult patients
(These books are available at the Mid-Manhattan library.)
I also reviewed a videotape of my clinical skills exam and practiced with someone to get a sense of time. If you can, try to review your tape with a faculty member.
I agree with medblazers' advice. Remember to address the SP's "hard" question appropriately and do proper reassuring, transitioning, summarizing, empathizing, counseling, and closing. Compliment the SP when they say they've quit smoking. One of the books says that everything that the SP does has a purpose. ie: if the SP acts uncomfortable, inquire about his comfort and how you might be able to adjust the bed to help him feel more comfortable.
Giving a good closing is also important, although I haven't found any book that gives a good example of closing. Generally, I said, "Mr Smith, in your history, you said you had symptoms A, B and C, and on physical exam, you had findings X, Y and Z. This could be consistent with diagnoses of 1, 2, or 3. We will order tests/x-rays 4, 5 and 6 to find the cause of your illness and to provide the appropriate treatment. Do you have any other questions or concerns that I haven't addressed?" And convey everything in layman's terms.
In retrospect, the advice that was given to me in the past (ie: all you have to do is introduce yourself, address patient, shake hands, make eye contact, wash hands, drape, simple closing) was inadequate. All the other components listed above are also important and may sometimes be overlooked in the rush to do a thorough H&P in 15 mins.
I hope this helps and don't feel bad. It happens to the best of us and is more of a reflection on the nebulous and subjective criteria of the CIS component. Good luck to you!