I'm new to ethereum, but as I see ERC20 tokens use the same blockchain as the main currency ETH. What will happen in case I send ERC20 complaint token to some ether wallet? I will "receive" them, but not as ETH... For example this transaction: https://etherscan.io/tx/0x42f7a2f62ef2f229b0d34fae09a89587c9a5e41c4283e13bb842170b956c483c OmiseGo to my parity wallet. It appears as 0 ETH, but how can I guess that OmiseGo was received via JSON RPC or some other method in my wallet?
Most tokens are immediately recognized by your wallet. If this isn't the case you can always manually check all tokens in your wallet on etherscan.io.
On this image you see that etherscan shows all tokens in your wallet. (This is a screenshot from an exchange wallet)
And if you want one of those tokens visible in your wallet you have to manually add them.
Most likely you need the contract address of the token. Depending on wallet used you may also need decimals of precision and Symbol.
You can easily get this information from etherscan by clicking on the token.