I read a ton of articles on how to be secure in crypto transactions when I started. The common recommendations are:
1. Don't use a public network while transacting.
Even better, never use them because there is a big risk that you will connect to a hotspot that is actually under the control of a hacker who can then steal all your login information.
https://en.wikipedia.org/wiki/Man-in-the-middle_attack2. Use strong, unique passwords. Don't use the same ones.
For each service you use, you should have a unique e-mail with a unique password, and of course a strong and unique password on that same service. This data should never be stored online or as plain (unprotected text) on any device.
3. Use a (paid) VPN.
I'm not saying that it won't be helpful, but what if most VPNs are actually just a cover for those who just want to spy on us that way? Regardless of whether it's true or not, the fact is that those behind VPNs probably keep a lot more of our data than they admit.
https://www.altcoinstalks.com/index.php?topic=324120.msg1626176#msg16261764. Invest in anti-malware, anti-virus, and anti-spyware.
Perhaps a good security suite would be the right solution - one that has good AV, anti-malware and of course a firewall. A lot of different security solutions from different manufacturers can sometimes be counterproductive.
5. If possible, use a dedicated device for crypto alone.
It makes sense, in fact it is recommended, but not everyone can afford two computers.
6. Use a secure browser.
What is a secure browser? I assume that maybe you mean one that is open source, and one that is not too destructive to privacy like Chrome.
7. Never click on unknown and unsolicited links.
Never, even if you get an e-mail from some super famous person who sent you a bunch of money and just wants you to click on a link to get that money

8. Enable 2FA in your accounts.
Good additional protection, but 2FA is not bulletproof - whether it's authentication via e-mail or SMS, so it's better to use other methods like authenticator apps.
9. Always check URLs.
Related to that
"don't click on suspicious links", and of course in cases where it is about very important (sensitive) links, each one should be checked in detail before entering your login information.
10. Spread out your funds.
This is smart, especially in the event that we are physically attacked and the attacker requests that we give him access to the wallet - a good wallet like some hardware wallets will always have the option of having more hidden wallets that can remain hidden in such situations.
These are also my non-negotiables and habits. What are your non-negotiables for secure transactions? You may have some uncommon ones that can be helpful to everyone.
Always check if the address to which we send/receive matches the one that is part of our wallet - in other words, beware of clipboard malware. Also, a BTC transaction must have at least 1 confirmation on the blockchain (preferably 2 confirmations) to be considered complete (irreversible). I mention this because of a possible double-spend attack, namely the same coins can be spent again if the previous transaction has not been confirmed.
+1