Have you seen this??
http://www.wgt.com/forums/p/55576/326107.aspx#326107
The table is a very good guide.
Also i have put a bit of sticky tape over power meter marked at regular intervals to assist with my driver and iron shots which also gives an excellent indication of putting distance as well. As far as direction is concerned i am yet to master that part of putting :-(
Putting is i'm finding very difficult for me but i have cut out most of the 3+ putts by using the tips in these forums and a bit of tape.
You will hear it again and again from those that know, practice, practice, practice.
I have also found St Andrews, due to it's enormous greens, is the best place to practice putting.
Hope this helps. Hang in there.