well, if you are talking about getting tokens absolutely free, you should try airdrops, you don't usually need to do anything, besides leaving your e-mail address, ERC20 wallet address (mostly), signing up for their social media accounts.
Some people here wrote that you can get tokens for free by participating in bounty campaigns, I can't agree less. When you participate in bounty, such as signature, for instance, you spend your time and energy, so I think it's far from getting tokens for free.