3. ENCRYPT YOUR MEMORY IF YOU ARE NOT 100% SURE IT WOULD NOT BE LINKED TO YOU. Especially if you are a valuable target.

Leaving your waifu pics on the USB to the picture that "this criminal" used as his profile picture is one way to get V&'d. Really rethink it hard. Your interestes, your documents, your photos, events, hints on your nicknames, OS, education, health conditions, entertainment, your opinions, your works and anything else - everything has a potential to help the police to link you to stuff and result in more warrants so be wise. It is not that tiring to use an encryption.

If you use unencrypted USBs/disks always make sure to wipe them after your files served their purpose.

You can use dd to force wipe the whole device with useless data after use, it is the most braindead command that will work on every Linux in existence that will wipe your stuff 100% of the times. (Though be mindful of that SD vulnerability of nano traces of shredded memory)

You can use "wipe -k /location/" command in terminal to wipe all data that is not occupied by files (so you wipe unused space clean and leave all files untouched), but you need to specifically install this functionality (I got it from AUR).

There is also shred functionality that lets you delete a file and overwrite that space at the same time. It is known just as shredding but it is not a defaults.

Read on these two if you are interested. They will be useful if you have old memory devices that can get you linked to them.
4. Using internet

Remember that there are 5 most important considerations when you make any web connection.
When doing something risky you must assess it appropriately and decide what you want to achieve from that interaction and safety measures.
There is no 100% anonymity, but there are anonymity vectors that you need to have covered depending on what they might do to you with the information that you provide voluntarily or involuntarily.

Important things you need to consider that I picked in particular will be listed below.
They will be visible to the server and depending on whether they want to log it: also to your ISP and any other owner of wires that the information will travel through who also decides to listen to it (that is why you encrypt your connections, I will later talk about it).

1. IP - exit node will always be visible (I will talk about proxies later). There is no way to avoid it.
2. METADATA LOGGING - depending on program and protocol some information will be shared (I will later discuss spoofing)
3. TRACE LOGGING - whenever your connection gets relayed there is a decent likelyhood that the path it travelled will be logged in one way or another, and traces can lead to deanonymization.
4. TIMESTAMPS - they mark when a data package and connections arrive. They can use it to prove it was you.
5. IDENTITY MANAGEMENT - they can observe that two seemingly separate people are one person, or one person is actually two. It is a long topic.

Additionally be aware of laws where you live.
Be aware that each time you make any connection outside your LAN then the outgoing IP, metadata, and timestamps will always be present. Additionally intermediaries like DNS, ISPs or other high level networks will have an idea of the trace of connection you requested from them - that will include your outgoing IP, data packets you send and receive with timestamps and depending on whether you use an encryption for your connection - it might also give up entire contents of what you receive and send. All people who observe and can read the contents (like the server you send it to) can also analyze your behavior and determine what kind of person you are, realize that you use multiple identities etc. Lots of info can be deduced using it.