How to Invent a Good Username

GENERAL ISSUES TO THINK ABOUT

• The most important thing is that YOU like your name. If you don't feel cozy with your username, it will irritate you sooner or later. However, especially if you are still young or new with Internet, be prepared for that your naming taste may change later and you may dislike that name you picked first! (That's something I have seen in the comments of this tutorial.)
  For example, my first online username was, if I remember correctly, my given name + my birth year (like, Lisa90, though my real name isn't Lisa), following the fashion of my peers. Later, I realized that this kind of name could be quite a hazard to my online privateness, as my birth year helps people to think how old I am (I was a young teen that time) and as my given name is some a bit rare, it could help nasty people to find me... Later, I adopted name Nuti after a story character of mine and its variation NuttyNuti. I have been really satisfied with my current name.
  Even if you can't help if your tastes change later, a good username in start usually lasts longer and gives better chances for that you like the name in the future, too! Changing an username is always quite a process.
• A good username is something that people can remember: thus, people can also remember you more easily! This consists of two main issues: clarity and originality. Clarity makes sure that your name is easy to understand and remember, and originality helps people to pay more interest to your username and tells you more easily apart from the other users. So, try to make your username readable and avoid copypasting mass usernames! (Examples later.)
• Also, try to think about what kind of impression you want to give to other users. What the name tells about you? You think for example these issues...
  Does your name look optimistic and happy or pessimistic and angsty?
  Is it a fun punny name or perhaps a mysterious fantasy name?
  Is it humorous or serious?
  Does it look like you a story writer whose creativity reaches to his/her username, too, or an uncreative mass fan who directly copypastes his/her (already hyper popular) favorite characters' name to his/her username?
  Is your username possibly revealing your nationality or hobbies?
  What kind of mental images or impressions it gives to other people? To with topics people relate your username?
  Remember that for example in dA your username may give people first impressions about what kind of art you do!

THINGS TO AVOID

• Too bombastic cliché words like darkness, angel, death, kami etc. Over-used, simply over-used. Also, they give easily an impression about you're talking bigger than needed. A healthy portion of humbleness is not that bad.
• Names of too well-known characters / series / phenomena in you username, like, Kakashi--Hatake or Bleach-Watcher or Anime-Luv. It binds you netpersona to that thing and makes more difficult for you to show your own self. Also, it makes you drown into the mass of people using similar username. And what do you do if you stop liking that character / what ever? Are you ready to change your username, then?
• Number lists. At least I find really annoying to see usernames like Catperson298109 or Nekochan087. It feels they are clones made of users called Catperson and Nekochan, not entire personality. Numbers can be used if they have a special meaning, like Awake24/7. But avoid using them telling your birth year, like in way Sleeka91: in the Internet, mostly people don't care how old are you, as long as you behave yourself. And on the other hand, some immature people may discriminate you due to your age.
• Cliché Japanese words like kawaii, neko, yami, shinigami, chan, kun, san and sama. Believe me; people are simply fed up with them. And about chans and other honorifics: Real Japanese-speaking people NEVER refer themselves with honorifics (unless they are weird), just people around them. So, using the honorifics like that is even grammatically wrong. Rarer Japanese words are okay.
• Banging your head into the keyboard - meaning totally random usernames like jdgskghki3ush. Honestly, people can't even remember your username if it seems like a line of random characters.
• Unneeded list of special marks. Almost nothing angers me more than seeing usernames like +*+~+InsertUsernameHere+~*+. They are NOT making them cooler, just more annoying to write! Also, extra X's are also frustrating to read.
• Things that doesn't suit you or that may give wrong information about you. For example, a buddy of mine has as a username Ainoboy. You may think it's a username of a male since the ending 'boy', but in fact Ainoboy is a female. Only people knowing some Finnish may guess her real gender: Aino is a well-known female name in Finland, and 'boy' gives some tomboy aspect to that. The username works well in Finland, but it causes misunderstandings in international sites. So, be careful when choosing the name!
• Also, usually it is better to start the name with a capital letter, AVOID WRITING ALL WITH CAPITALS, and aVoId LeTtERiNg LiKe ThAt. With _short_ names, they can be used.

SOME GOOD NAMING METHODS

• Funny and/or not-too-used real words or phrases. What about a username, like, Haphazard? Isn't it sweet? And carefully/funnily chosen adjective + substantive combinations or other combined words can create useful names. For example, StripedBanana and Levitating_Sheep are nice names in my opinion! I've also seen here artists with usernames RoughArrow and Elves-Ate-My-Ramen, and I think that they are nice names! Just avoid clichés mentioned above and choose name that suits you!
• The previous one, in your own mother tongue (if it is not English). A nice spice, and it hints quicker to your fellow X-landers where might you be from! Thus, you can start quicker to discuss in your own language!
• The previous one, in some other language. But be sure that you know ALL meanings of the words you use to prevent embarrassing situations with people talking that language! Also, check out the grammar you need with the name (like, genitive) and avoid too-used words! (And be warned about people that think you may speak their language.)
• Fully or partially self-invented names. Think like naming a fantasy creature. My own often used username, Nuti (sometimes combined with word Nutty), falls to that category. Also, derivations from real words/names are good, like 'a violet' -> Violetu. (And yes, Nuti is not derivated from word 'a nut', or so I think.)
• Not-too-used things relating something you're interested in. Thanks for the idea, Lady-Madbeth! She told me she finds easily people that are interested in classical literature, since they comment like, 'how, your username brings my mind Shakespeare.' Be warned about too common topics (like, Anime--Luv), but instead, give hints about what are you interested in. For example, a deviant that likes taekwondo can use username like 'AnnunSogi' (a common stance used in taekwondo, also known as horse riding stance). With that, you may find people interested in the same stuff as you!