What is the best payment method online?

Skype

That depends on where you want to pay and for what you want to pay.

My favourite and the one I use when- and whereever possible is paysafecard. It's a prepaid card where you do not need to enter any personal data and it does not require you to pay any fees, so it's safe and for free. I use it for online games mostly, sometimes for Skype.