One quick tip: use stainless steel screws !
On the picture on the left you can see two screws. The first on the left, attached to the wall is made of stainless steel. The other one on the shower head, in the middle is (was) made of some other shiny metal and is slowly rusting away. I cannot change the shower head angle anymore and I surely will struggle to replace it.
So next time you go to the hardware store (or buy them online) because you need to change one in your bath tub, shower or anywhere exposed to moist air, remember to buy stainless steel screw. They're a little pricy but will last much longer.
While I'm at it, remember to changing non stainless steel screws before they rust away or you will have a really tough time to replace them... if you manage to...
I personally prefer PZ2 screw heads but that's just a matter of taste: