Everything that everyone has said is good advice. I had an examiner say that the IFR ticket is that hardest whereas the CFI takes the most preparation.
Some things I would suggest is, (some of which were already stated). Stay ahead of the airplane. That means 4,5,6 steps ahead. Anticipate what is next.
Have a procedure for you approach set up and do it the same way everytime. Slow flight and basic attitude inst. flying is a great exercise. Small corrections. Something I incorporated from an article I read is to fly the approach visually, without the hood. That seems to really help some people.
Hope that helps.

Papa T