My phone does not charge, how do I troubleshoot?

I would see if it was with both ac charger and usb

then I would try with another cable and usb port / ac charger

if non of those provided any success then I would suspect a broken connector or a defect battery

Try these steps as needed

1. Charge with AC adaptor

2. Charge with OEM Apple cable, not knock-off cable. Get anothor cable if you already are

3. Clean Lightning connector dock, by blowing out with canned compressed gas (NEVER by mouth), and electronic contact cleaner

4. Restore iOS in iTunes

iTunes: Restoring iOS software

5. Get service from Apple or Apple authorized service center