Airdrop, mining. I signed up for airdrops. But only a few of them gave me tokens, which are in small amount and are of almost no value. I have been mining Pi network. But I doubt it will ever be tradable on exchanges. So I do not find these methods as a good way to earn tokens. Rather I find bounty campaigns a good way.
Airdrop these days are not that popular, My suggestion is avoid it because, it can be a waste of time or it can lead you to losing your money or your private information. First, if you click a phishing link it can hack your PC or your wallet (if you are using a web wallet). And if that airdrop is demanding a KYC you can lose your private information there and it can be use in illegal activities.
I find bounty campaigns a good way.
Regarding bounty campaigns, it's very hard now to see a legit one or a promising one. Some bounties even though they have a great background and great objectives they are turning out to be a scam, So I think be careful to those campaign, if you find a good one then, you are very lucky!