Unless you are prepared to do considerable research into the ICOs you are considering participating (or have extra money to burn), then the best bet at first is to seek out airdrops, where tokens are sent to your wallet for free. In addition to the sources mentioned above, you can also look for airdrops on twitter (
https://twitter.com/cryptoairdrops?lang=en and
https://twitter.com/airdropadvisor?lang=en are decent). While you are applying for airdrops you will earn about various ICOs and the tech behind them until you have enough knowledge to invest wisely.