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Sometimes I get home and need to go out again soon and only have a short while to charge up my phone before I leave.
Any tips or tricks on how to charge my phone any quicker?
I don't want to have to mess around with the charger or the phone (iPhone if that is needed for the answer) so please avoid these answers!
There are numerous things you need to know about charging your phone in order to charge it any faster.
So check the wall adapter that came with your phone so you know which power source is fast enough for maximum charging speed. It should state how much ampere (SI unit symbol: A, often shortened to amps) the output got. Most common smartphones "need" (for fastest charging) 1.0 ampere, newer smartphones "need" 1.5 ampere and tablets even "need" 2.0 ampere.
Turning your smartphone completely off increases charging speed to a maximum.
(these tips are also handy if you simply want to make your battery last longer)
If your smartphone drains the battery faster than before it could be a sign of the battery itself dying. This just happens; batteries have a limited lifetime but discussing how to increase battery life is a different topic.
The iPad charger will charge your iPhone faster than the iPhone charger that came with the phone.
The iPad charger puts out 5.1v at 2.1 amps.
The iPhone charger is 5v at 1 amp. 
The larger of the two is the iPad charger.
Short-circuit the USB data pins on the phone side, that's what the most powerful chargers do to tell the phone that it can draw the max amount of current without needing any digital negotiation (otherwise it would negotiate with the OS and only get 500mA).
From Wikipedia :
on a dedicated charging port, the D+ and D− pins are shorted with a resistance not exceeding 200 ohms ... A dedicated charge port may have a rated current between 500 and 1,500 mA
I've built my adapter myself using two USB connectors (male and female) soldered by their power pins and the data pins bridged on the female (phone side) connector (the male/PC side data pins aren't connected) with a bit of heat-shrink insulation to protect it and hide the horrible soldering.
Although this is against the USB standard, I have yet to discover any issue with it; all my devices work just fine and didn't go up in flames and in theory that shouldn't happen as there is over-current protection on the ports that will just shut down the computer if too much current is drawn. I'm saying in theory, just be wary of crap chinese gadgets with USB ports, as these ports have no such protections and may very well catch fire.
Lots of nice answers here, some uninformed answers as well, but I think that most of them miss the actual point.
Background:
First thing that needs to be understood is that device called "charger" is nothing more than a dumb power supply. It has no intelligence beyond the SMPS controller, which tries to maintain output voltage as current requirements change.
The charger itself is inside of the telephone itself and its operation can not be easily affected by the user.
As others have mentioned, it's actually important to know how fast the phone can charge, that is to say what is actually the maximum current that the charger will take. The charger will monitor the actual battery state and it's up to it to do the "smart" part.
Power supply:
For fastest charging, the power supply needs to be able to provide as much current as the charger needs to charge the battery, plus all the current the phone itself needs to operate. That's why we have answer saying that turning phone off will speed up charging, since this way we minimize the power used by the telephone itself. It would be nice if we have some percents more than phone's maximum consumption, just to be safe.
Next step, and the one most important, is getting the charger actually to tell the telephone how much current it can produce.
As I previously mentioned, chargers are dumb, so there's nothing to actually talk to, and USB is basically being abused to carry high current. We do have some standards for charging over USB, but they were all bolted on the basic USB 2.0 standard as afterthoughts.
Then we have the "smart" telephone/tablet manufacturers that are unsatisfied with standard options and want to have more choice. That's where most of the difficulty comes from. We already have one answer mentioning the Charging port specification and it is there where the main issue is. The pre-standard ways of negotiating higher currents are still there and are still making problems. Apples iDevices still use their resistor dividers to set the maximum charging current and those specifications can change over time (compare previous link with this). Furthermore, other manufacturers are pushing their own standards. Here is a picture for Samsung for example.
So we need not only a high current charger, but we need a high current charger that will be recognized by the phone.
Unfortunately, with exception of using the newest and greatest OEM chargers, there's little that can guarantee that a a power supply will be correctly detected by the phone. Some power supplies may mention how are they wired on the inside, so that may make the decision a bit easier for the end user. Otherwise, all that's left is looking for reviews and experimentation.
Cable:
Finally, there's the part of getting current from the power supply to the telephone. One big problem with USB micro cables is that they tend to be thin! This can be a considerable problem for charging phones. A USB 2.0 cable will have on the inside at least 4 wires, and to pack those wires in a thin cable, the wires themselves need to be very thin. Then we have a problem of resistance of those wires. Quite often, it can be neglected, but in case of USB power supplies and micro cables, we are reaching the point where cable itself may be dissipating non-negligible amount of power and is affecting the output voltage at the device connector. In general, if we have telephone whose charger allows fast charging and we have power supply that can provide enough current, cable may end up being the limiting factor. Phone's charger is not perfect and it needs a bit of head-room to charge. Also chargers will often lower charge current, if they detect that the power supply voltage is sagging. Some experiment results published here tell us that iDevices will ramp down charge current based on voltage.
So let's take a look at some numbers and cable marking. Here's a handy calculator for voltage drops. Let's assume that our charger will provide 5 V and can supply at least 2 A without any voltage droop. I'll also post results for calbe lengths of 3 and 6 feet.
Traditionally, the thinnest USB cables will use a 28 AWG twisted pair for data and two 28 AWG wires for power. Let's take a look at some results with that cable.
At 3 feet length, we have output voltage at the end of the cable of 4.22 V. With this, we're already out of USB specification. If we take 6 feet, that gives us voltage of 3.44 V at the output of the cable. Our device definitely won't be able to charge at high current using that cable!
I we move a bit up and use a cable that has 24 AWG power conductors, we'll have output voltage of 4.69 V at the end of the cable, which is just good enough, but some devices will ramp down their charge current with that. If we go to six feet, we'll have output voltage of 4.38 V, which is outside of standard.
If we move again up a bit to 20 AWG for power conductors, we'll have output voltage of 4.88 V at 3 feet length and this should be OK for charging, but iDevices will still ramp down their current. At six feet, output voltage will be 4.76 V, which is still OK.
I've heard that there are also USB cables that use 18 AWG wires for power conductors, so let's take at some results with that: 3 feet gives us output voltage of 4.923 V, which is quite good and at 6 feet, we have 4.85 V at the end of our cable.
This is also explanation why some "chargers" have nominal output voltage of 5.1 V, even though the standard calls for nominal output voltage of 5 V. With 5.1 V, our 3 feet 20AWG cable will have 4.98 V at its output, while our 24 AWG cable will have 4.79 V at its output.
There are even special charging USB cables. Their magic is very simple: They are short and may use thick conductors, minimizing losses in the cable itself.
Bonus: How to interpret USB calbe markings: Some cables may have inscription on them such as 28AWG/1P+24AWG/2C. First value is about the data conductors. We have one twisted pair of 28 AWG conductors for data. On USB 3.0 cable, we may see something like 28AWG/3P. Second value is for the power conductors. We have two (non-twisted) wires of 24 AWG. The higher the second value is, better is the cable for charging.
TL;DR: Determine maximum charge current for your phone, get charger that can provide that much or more and is wired for fast-charging your phone brand and get a short, thick USB cable for connecting phone to the charger.
There really is no "fast" way to charge your phone. Via a computer, USB3.0 charges faster.
You could buy a power bank. You can just leave it charging at home, and then take it later and use that to charge your phone. There are also some "on the go" chargers where you can put AA batteries in and use that to charge your phone.
You could turn off the phone, while it is charging, so it doesn't consume power. Or turn it into airplane mode+turn off all not needed applications.
Other than that, there is no safe way to recharge your phone "fast".
You could also buy a phone that has changeable battery itself.
Something else to take into consideration, not really mentioned in any of the other posts, but does affect how fast the phone charges: Even if you had a charger capable of delivering as much current the device was wanting to draw, there is still a limit on charging speed that boils down to how Li-Ion cells charge.
Most cells are happy (And by happy, I mean not-catching-on-fire) to be charged at somewhere between .5 and 1C, where C is the capacity of the battery with the units mangled. For example, my phone has a 2600mAh battery. Ideal charging rate would be somewhere between 1.3 and 2.6 amps. However, Li-Ions are also very temperature sensitive, which can lead to the not-happy fire scenario mentioned before, so most charge controllers also limit current when temperatures get too high. In most cell phones, I imagine the charge rate falls more towards the .5C range of things due to temperature constraints.
Now, on top of all that, that's not all. The .5-1C charging is only good for about 70% of a Li-Ion charge cycle. Li-Ions also do not like going much above their rated voltage (somewhere around 1% or less, I think), and the voltage on the cell will rise as it charges, eventually reaching 4.2V. Once that point is hit, the charge controller will hold the voltage, and decrease the current, which is shown on the dotted vertical line on this picture.
This is the reason why it always seems to take forever for your phone to charge for that last bit (I'm not exactly sure what drives the recharge rate in the constant voltage section of charge. I'm sure fun electrochemical stuff).
So, the takeaway from this is your device will only charge so fast, regardless of how much current you can supply it.
All USB devices are designed to work at 5V of voltage. Standard USB 1.0 and 2.0 current intensity is 0.5A but there are chargers which allow up to 1A current intensity and are still safe for the devices. With this higher intensity charging will be faster. If your charging is extremely slow it might be a problem with the cable too. You can try to replace it and see if that helps.
You could use a handy power bank which could charge your phone anytime anywhere.
This video has some very good hacks that you can use, especially in emergencies. You can charge you phone fastly when it is in safe mode because most of the unwanted process gets stopped. Remove your battery from phone and charge it! In that video I have showed some methods for charging your phone when there is no power.
