There's a lot of discussion about the obvious steps that you need to take to protect your identity, changing your IP address being the favorite one. Whatever technical measures you implement to stay anonymous won't matter for squat if you can't eliminate similarities between identities. You might think "tons of people will share this with me so it's not important." That's flawed and I've seen it get people pwned.
1) Never use social media except to contact people you wouldn't otherwise be able to contact. If you don't have somebody's number then contact them on Facebook. Don't have your conversation there because it will be stored online permanently.
If you use social media you will make it much easier for somebody to build up a profile on you and compare it to online personas.
2) Never use the same websites under different personas. You can grant an exception for heavily trafficed websites like Wikipedia. If you contribute to Wikipedia science articles under your real name, you could edit hacking pages under your persona. Be very careful and I don't recommend it because regular Wikipedia users might get a "feel" for you and be able to spot the connection.
Don't assume that just because there's 30 different users on Derp Dobson's forum that you and your persona will appear to be different users. You won't and the connection will become obvious very quick.
3) Don't use the same hacking tools between identities that you made yourself or were made by some random dude on GitHub. The two of you didn't just happen to find the same tool.
4) Watch your coding style. Tabs versus spaces, indent style, and code brace style can correlate to you.
5) Learn common grammatical mistakes and start making them. If you're 1 out of 10 people who gets a grammatical point right, you just narrowed down the possibilities of who you can be.
6) You will encounter the same people under different personas. Make sure that your own brother wouldn't recognize you.
7) Learn about all information that gets sent by your browser. If you use a tablet that flopped and has a unique screen resolution then in can connect multiple identities.
Never write off a similiarity as "other people will have it too." One connection is all it can take for somebody to make an intuitive leap.
