Assume that whatever you have done you aren't anonymous. No way to know how far browser and hardware fingerprinting has come behind closed doors. If people who don't work for the NSA have shown that your computer is uniquely identifiable by the cluster of fonts, plugins and hardware then the government has either logged us all already or in the process of doing it.
Exactly, I have spent a little time playing around with what type of information can be gathered from a machine loading a webpage. When you combine fonts, resolutions, versions, flash, cookies, language etc to produce a machine fingerprint you can get pretty close to uniquely identifying a single user within a restricted subset. TOR doesn't protect from this. Now if you add in the fact that you can be identified by your browsing pattern as well (all of us will have a large number of sites we visit regularly and those follow us even if we change device, my list will be different to yours and we can be identified by it if someone is familiar enough with our habits) then you get an idea of what you are up against in order to actually acquire anonymity. As you say, assume you are not anonymous. Even if you are right now there is nothing to say that some future time will see a consolidation of various databases containing historic browsing records allowing some future snooper to figure out what sites you visited today.
Please keep in mind that everything you send through Tor is decrypted at the exit node. Don't send anything that could be linked to you through Tor. Disable Javascript while using Tor, it can leak your IP. It's a network that works beautifully if you know the basics of how it works--if you don't, it becomes much less useful.
WHERE IS OUR CLICKBAIT SPOILER / HIDER EXTENSION?!
I'm not too worried about going anonymous. It isn't that I don't believe anyone has the capabilities to exploit me, I'm just not nearly interesting enough to be a prime target.
Just use Whonix. It uses a set of virtual machines to route all your data through Tor, so you can use anything on it, such as javascript, flash, whatever. You'd have to mess up real bad to leak your IP on it. Apt-get over Tor is a little annoying, but only the first update. As an added bonus, you don't need to reboot like with Tails.