disassemble your device carefully (if you're not sure, there are a lot of disassembly tutorials for almost every device out there) and identify the +5V lead on the USB port and follow it to a comfortably solderable spot (unless you are super skilled and equipped and can solder a single micro USB pin) don't worry about the ground lead, every piece of metal in there is grounded.



in my case (galaxy s II), disassembly wasn't hard, 7 screws and a pry tool \ pick \ fingernail and it's open.



finding a place to solder was a little more challanging, it needs to be a place with enough room for the wire and not too small and delicate for the soldering iron to burn or damage.

i used the capacitor shown in the pictures (i had a little help from google and a multimeter finding it).



after you found your soldering spot, try and find the best path for your lead, it has to connect the + from the coil to the + on the USB.



in my case. i chose to work with copper foil because there's just no room for a wire running along the side and the copper foil is relatively easy to work with.



the main consideration for me when choosing the path was that i wanted the phone to seem (almost) unaltered from the outside and for all the separate parts to stay separate (i didn't want a wire or something permanently connecting the board and the cover).



finding ground :

pretty much every piece of exposed metal should be grounded.

you can check with a continuity meter to see whether a specific piece is grounded or not.

it does not matter what it is you're connecting to, as long as it's connected to ground.

choose the piece that will make your design as simple and as neat as possible.

if no grounded piece of metal can be found you can connect to the USB port ground pin.