Common methods of money laundering include smurfing, shell companies, trade-based laundering, and digital currency transactions. Smurfing involves breaking up large sums of money into smaller, less suspicious amounts. Shell companies are entities that exist mainly on paper but conduct little to no business operations. Trade-based laundering uses trade transactions to disguise the illicit origins of money. Digital currencies, like Bitcoin, offer a new frontier for laundering activities due to their relative anonymity.