Standard Heights?

(I posted this also in the bathtub forum since I didn't know which it should go in)

Could someone tell me a general rule of thumb for the heights on these:
(from finished floor)
1. Shower Head, Spout, Handles (this is for a shower/tub that is 20.5" high)
2. Tile in a shower(since I don't want to go all the way to the ceiling)(8' ceiling)
3. Wainscotting
4. Electrical boxes(switches, outlets, etc.)

Also if I don't go all the way to ceiling with the tile, does the shower head come out of the gwb or the tile? Is one more preferable? Thanks.

heights

The valve and shower arm are mounted at a convenient height. Usually a shower only valve is mounted about 42" above the floor, but a shower/tub valve is about 10-12" above the tub. The tile can go whatever height you want it, and the shower arm can come through it or above it. There is no preference. Electrical switches are usually mounted about 42" high, but some newer houses are set up with them lower for use by children or physically handicapped persons. Electrical outlets are usually 12" high, unless you are referring to those above the countertop.