Operational Security is a lifestyle, not a setting. Compliance with the following rules is mandatory for survival in the darknet ecosystem.
Never, under any circumstances, paste a plaintext shipping address into the order box. Even if you trust the market, you should never trust a database. Always encrypt your address with the vendor's public PGP key before submission.
Use the TOR Browser on the "Safest" security level. Disable JavaScript where possible. Never resize your browser window, as this provides a fingerprint of your screen resolution.
Never send funds directly from a KYC exchange (Coinbase, Binance, Kraken) to the market. Use a "cleaning" wallet like Cake Wallet or Monero GUI. Transfer from the exchange to your personal wallet, then to the market.
Your username should have zero connection to your real-life identity, email addresses, or handles used on Clearnet platforms (Telegram, Discord, Reddit). Use unique handles for every platform.