If your TouchID is feels sticky or isn't working right, don't take it to a shady shop to get fixed (that can seriously mess up your iPhone.) Instead, you can use a Q-tip for its intended purpose with a little bit of rubbing alcohol to get your home button working like new.
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There's a lot more information on this Apple Support thread.
If your iPhone is charging slowly, one problem it could be is that lint is packed into the corners and sides of the Lightning charging port. One thing you can try is to use a skinny tool like a toothpick to remove all the crud from it.
This is how much lint was removed from a single iPhone.
If your phone's earpiece sounds like it's too quiet, there's a good chance lint is simply in the way. You can rub a pencil eraser over your speaker's grill to clear out debris.
Apple suggests you use a "brush to gently clear any debris from the speaker," which is certainly more sanitary, but less fun. One person on the iFixit forums helpfully suggests you can put your mouth over it and suck a little for a tool-free fix. It's gross, but it works.
In general, if your iPhone is a little bit too quiet, especially on speakerphone, you can amplify it by placing it into a bowl.
Apple's Earpods tend to fray in two places: near the earbud itself and by the 3.5mm jack. You might be temped to throw your pair away but they're easy to repair with Plasti Dip. Tape off what you don't want to get covered in rubbery plastic and dip your headphones in.
The process works great for charging cables, too. Alternatively, you can use Sugru, a sticky putty-like "moldable glue," to patch up cables as well. It can also replace the little feet at the bottom of your laptop.
Sugru is available from hardware stores and Amazon. More tips on this kind of repair over at Lifehacker. Lots of additional information from Sugru.
Sugru can also be used to put fun "bumpers" on your iPhone if you don't want a case, but want to be sure its screen won't immediately shatter when dropped on a corner.
Instructions here.
Prevention is better than repair, though. If you've got a spring from an old pen, you can make your iPhone cord significantly less likely to fray.
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If you need instructions for this hack they're over at Instructables.
If you need to stand-up your iPhone, you don't need to spend $20 or mor on a dock. Turns out, a basic binder clip or two makes a great stand.
You probably don't need directions, but lots of them are available at Instructables.
It's also pretty easy to make an iPhone stand with an cut up credit card or cardboard.
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If you ever find yourself in need of a stylus, it's pretty easy to make one out of anything that points and a candy bar wrapper.
All you need is an old pen, a sponge, and some chewed gum. It's not pretty, but it works. Instructions for a deluxe version is available on WonderHowTo.
Lots of people will tell you that if you get your iPhone wet you should put it in a bin of rice. Even better: save the bags of silica that come with new shoes, and use them to dry your iPhone when you accidentally drop it in the sink.
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If you need to change the SIM in your iPhone, you don't need a specialized tool. A paper clip works just fine, according to Apple.
Here's the official support page.
