Powering arduno

Hello, i have a question, can i power my mega board from the battery of a car? Or should i but a phone charger and power it through usb? Or a 12 v regulator between car battery and the mega board?

It depends on what all (besides the board) you are planning to power. There are some nice little switching supplies that will take 12v in and give you 5v out with pretty good efficiency for a reasonable price (even Amazon carries them).