Source: Romuald Jay
iPhone is an incredible machine,but when everything goes wrong it's hell. Here are some tips, that will help you solve the most common problems.
1) I lost all my contacts!
Re-import those who are in the SIM card. Go to: Settings / Mail, Contacts, Calendars / Import SIM Contacts.
2) My touchscreen is crashing for no reason!
It might be the case that your touchscreen might act out and not let you start apps. This is caused by the proximity sensor. The sensor is malfunctioning, and is wrongly detecting the phone as always being in call mode. You must tap the phone at the top left side of the device. Restart the iPhone and voila!
3) My iPhone fell into water
First thing you need to do is turn it off. You must then wait until all water has evaporated before turning it back on. Speeding the process up by using a hairdryer is not recommended. You should rather leave your phone in a warm room, with a temperature not exceeding 40 Celsius degrees. After a day or two, you can try turning it back on. If the water in question is pure, the odds of your phone working are higher. An iPhone that falls in seawater is less likely to work again.
4) How to recover a completely crashed iPhone?
Switch to DFU mode. Connect the iPhone to the computer and start iTunes. Press and hold the main button-Home button-and the "On/Off" button for 10 seconds.
After these 10 seconds, release the "On/Off" button but keep holding the main button until iTunes displays that it has detected an iPhone in recovery mode. You should then release the main button. To exit DFU mode, disconnect the iPhone and press the "On/Off" button to restart it.
5) What to do when your iPhone screen is blocked?
Some users have their very own solution: "tap 3 fingers on your screen for 2 or 3 consecutive times, but not too hard."
6) I lost my apps after an update!
Open iTunes, connect your iPhone, click the "File" menu and transfer your purchases.
7) The "Home" button doesn't work anymore!
Try calibrating your "Home" button.
Open an app-doesn't matter which one- then press the "On/Off" button until the "slide to power off" slider is displayed. Release the "On/Off" button, then press the "Home" button to return to the home screen.
This procedure calibrates the "Home" button. If the problem persists, it could be a hardware issue, resulting from dust inside your phone for example.
8) My iPhone won't turn on!
Try resetting it. Press and hold the "On/Off" button and the "Home" button for a few seconds until you see the Apple logo. It could be that your battery is drained. So before that, recharge or connect you iPhone.
9) Ever since I installed iOS 5.0.1, my iPhone keeps rebooting, what can I do?
Remove the SIM card from your phone. Activate 3G and Cellular Data and reinsert the SIM card.
10) I can't connect to the internet, weird uncontrollable issue!
In iOS4, there are some wifi connectivity problems where certain conditions apply. If, after having tried the solutions put forward in this chapter, you still encounter the issues, you must update the phone. These problems were solved by Apple with the iOS5 update. Updating your system is therefore a more reliable solution.
All these tips are from «99 Forum Found Tips and Tricks for my iPhone». The book brings together the best tips and tricks posted on international iPhone-dedicated forums. The author browsed through forums looking for the best solutions for the problems you could face with the iPhone. He selected only the solutions that have been vouched for by forum users. The book is available on iTunes and Amazon.