http://sparrowa7io5pz6ud3ehqzosvepbxbxt2zphmkjsylp2zgxooko23pqd.onion/docs/spending-privately.html
Some, like the fake two person coinjoins discussed here, create transactions which introduce confusion (or entropy) in the transaction graph.
Others, like payjoin, break some of the assumptions that common heuristics depend on.
Used together, it is possible to remain relatively private when transacting with Bitcoin.