How do you get free World of Warcraft or runescape membership for free

You don't get RuneScape membership for free (except perhaps, by definition, a "membership" in RuneScape is additional privileges you get for paying a monthly fee).

I don't know about World of Warcraft, but the situation is probably similar.
If any Web site or players promises free memberships, it is surely a scam.

However, there are websites that allow you to complete surveys for money which can then be transferred to your paypal account.

It takes only a few hours to be able to afford a membership. The processing normally takes around 2-3 days.