A:
I achieve best results when I charge with their USB cable and an AC power block. However, I usually charge mine on a generic cable from Walgreens or my LG provided cable for my phone, usually in my car on a 12v converter. The biggest difference I've found is that a full charge from dead on a 12v car charge takes between 2 and 3 hours, where with a 120AC at home it takes between 1 and 2 hours.
For a maintenance charge on ANY rechargeable battery, you want to let your battery drain completely and charge on AC generally overnight. This helps maintain the life of your battery and prevent an overvoltage occurrence. (Which can damage your battery and potentially kill your device.) Always remember to turn off any device that houses a rechargeable battery when doing a maintenance charge (Like this handset!)