You didn't supply much context to your question, but if you are already exchanging with someone, for example by message or email, it could sound odd to say "before meeting online". It wouldn't sound precise because you would already have "met" them to a degree via text exchanges. You could say:
Do something before our video call
Do something before our first meeting (this is ok because a "meeting" would be understood to be something that is scheduled.)
Do something before we skype.
But if there had been very little prior communication, a student could say, for example,
"Thank you for accepting my lesson request. I look forward to meeting you."