#1: Remove shower head.
#2: Place shower head in bowl or bucket large enough to submerge shower head.
#3: Fill bowl or bucket with enough cider vinegar to cover shower head.
#4: Wait for it.
#5: Occasionally test shower head before dumping out vinegar.
Dip it in CLR like the commercial shows you
You can clean your shower head with whatever you want - white vinegar just dissolves the hard water minerals and gets rid of those white deposits.
Lime away. Lime away does not work on hard water deposits.
Shower heads lose their effectiveness when they become clogged with mineral deposits, especially in areas with particularly hard water or well water. Metal shower heads are more prone to corrosion from hard water. You can extend the life of a metal shower head by cleaning it regularly. The best way to do this is to put one to to cups of a 50-50 white vinegar/water solution in a plastic bag. Position the bag so that the shower head is submerged in the vinegar water. Secure the bag with tape to the shower head nozzle. Leave it there overnight to dissolve the mineral deposits in the shower head.
Hard water is a term that means the water has lots of minerals - hard water stains are solid deposits of those minerals left behind when the water evaporates. The water initially dissolved those minerals because it was acidic - a weak acid such as lemon juice or vinegar is usually pretty good at removing these stains; or a scrubbing paste made of baking soda and water.
If the clog is due to hard water deposits (instead of food) I suggest you try CitriClean. It was designed to clean hard water film and deposits off of dishes and dishwashers. It uses a chemical process called chelation. Search for "CitriClean of Florida"
Metal shower heads look nicer but show hard water, plastic will not show hard water, if you have a water softener a metal shower head is the way to go.
It shouldn't be ideally, as hard water deposits limescase (a solid) in the boiler
Mineral deposits.
White residue on faucets and shower heads most likely are from the hard water mineral deposits that your water contains. Sometimes, the residue is from cleaning products, but most often not. To help reduce white residue and hard water stains, a salt type water softener is recommended.
High pressure shower heads will hold up best to hard water. However, regular cleaning is still advised.
SWAG
Ugh.. now here's a real pain in the neck problem. The best thing I've found is to soak old towels in pure vinegar and lay them on the tiles over night, then scrub the next day. The acid in the vinegar will break down the minerals so they can be scrubbed off. The towels keep the vinegar from drying up before it has a chance to do it's job. The biggest problem here is that the hard water stains will just keep coming back, unless you find a way to prevent them. A water softener will help some, but it won't fix the problem. I clean houses for a living and have a customer who has good success with a shower spray product made by Arm & Hammer called "Clean Shower Daily Shower Cleaner." You just spray it on when you are done showering and it keeps the shower looking good. My Grandmother had a well when I was a kid and she kept her shower from getting hard water stains by wiping it out with a tile every time she got out of the shower.