Which is the technique to avoid transactions link to a wallet?
Use your UTXOs separatedly, and use change addresses, and use Bitcoin full node, with Tor connection if possible.
More information on privacy of your transactions.
Bitcoin privacy resources.General guidelines for sending BTC transactionsDon't send round numbers
Don't send round amounts. Instead of sending 0.1 BTC, send 0.10125
Use Bitcoin Mixers
Mixers add an additional layer of privacy to a transaction to avoid exposing user identities.
Avoid reusing wallets
Don't send your Bitcoin change to the same address you use for sending bitcoins.
Avoid including many of your addresses in one transaction
Any time you can, try not to send BTC from your various Bitcoin addresses.
Avoid using "send everything" option
If you are withdrawing funds from an exchange, it is okay.
If you're moving funds to another wallet, do not transfer the whole amount to another address. It greatly compromises your privacy.