I believe I managed to understand.

The correct and network safe way to make a 0.3 BTC transaction is to follow these steps, correct me if I'm wrong.

Example: My UTXO is 0.9 and I need to make a transfer of 0.3, after this transfer there will be a balance left and what should I do after the transaction is generate a new address and send the rest to this new address? so i have a new UTXO of 0.6 btc?

And that?