iPhone, iPod, iPad repair checklist
So one day you wake up to use your iDevice only to find it's really not doing what it's supposed to do, is it hardware? Is it software? Is it a temporary glitch? While this checklist won't magically fix things, it will give you an idea of what you are facing up against.
First things first - do you have your iDevice backed up via iTunes? Have you also made a copy of your contacts, photos and videos to alternative backup locations ( as opposed to just iTunes )? If you don't, then doing anything beyond here might result in some loss of data depending on what's wrong with the iDevice in the first place. The following series of tests are something that all faulty iDevices are put through here at CTPC when we're dealing with the unknown.
It's important to know, with iPhones in particular, that so long as the single main circuit board is alive and functioning, you can replace and/or repair everything else. The worst kind of failures for iDevices is when their flash-RAM ( NVRAM ) develops a fault, because it takes all your data with it. There are some recovery options for NVRAM failures, but they're not cheap, as it requires a very professional recovery process ( thousands of dollars to do ). Having a failure in things like the display, graphics, audio, SIM, wifi etc are all a lot more tolerable, since you can still get the data off the machine and you're then only having to endure the cost of a replacement device.