Q. Can I put my wonder board up without a moisture barrier?
A. NO
The biggest and most common  mistake is not having a moisture barrier. Without a moisture barrier

you can get  into big problems , the reason why is as time goes by moisture builds up in between the 
walls and can cause molding problems.

Q. Do I need blocking between the studs?
A. Yes
You should always put blocking in between the studs to give the shower walls strength and to protect the hot mop from damage and for the shower pan to have support.

Q. Do I need a damn?
A. Maybe
Depending on the type of shower floor. Whether it is a handy cap shower or a regular shower with a dam, by state code their should always be a minimum of two inches from the top of the strainer to the top of the dam. A handicap does not require a dam if the sub floor of the shower pan is taken down  and the strainer is two inches 
below the main floor of the bathroom floor.

Q. Can I just build a dam out of concrete?
A. Maybe
You can, but its best to build it from wood.  This is best way because its faster , easier, and you will have to put nails or staples on the outside of the dam to hold the diamond wire-latch.

Q. Can I put nails below the dam?
A. No!!
By state code you can only put nails two inches above the dam.