Even with a number of posts, threads, reputation points, uploads and accounts wiped out by the mini-cataclysm on Fakku, I felt that this thread deserves to be created once more, due to all the useful knowledge one can gain. :D
The following are guides I have obtained, courtesy of anonymous from 4chan, though I did correct a couple of spelling mistakes and grammatical errors. Without further ado, here they are:
[color=red][font=arial black]Yandere Guide Part 1 - Finding One:[/font][/color]
We've all seen it happen in games, anime and manga, but how do we know it's not happening to us? How do we know that we're not being targeted by a yandere who wants desperately to be ours? I'm going to help you find your Only True Love.
1. Nice or sweet girls have a higher chance of being yandere.
2. Pay close attention to the girls you find yourself coming into contact with, even if it's seemingly harmless or irrelevant. The yandere is quite driven to make contact, but her overriding paranoia will make her subtle.
3. Once you've established likely candidates, try talking to them. If she drifts out of the conversation or if you sense she is getting bored -- it's not a yandere. While doing this, keep an eye out for girls watching you from the sidelines.
5. After establishing a rapport via conversation, ask the suspect(s) to come to your home. The yandere will always agree -- however, a non-yandere who happens to like you may also agree to this.
6. When you get her in your home you have to test her. How eager is she to do that extra mile to make a good impression -- pushy offers to cook, clean, or do something else, typically with a subservient attitude, are all positive signs of yandere-hood.
7. The yandere will be the girl who you notice coming over to visit afterwards on innocent pretexts, usually wanting to do chores for you as she feels doing this will entrench her into your life.
8. Confess to her. She will agree immediately. Many yanderes can be found out at this stage if they lose their self-control and become sexually aggressive.
9. If not already discovered in the last step, try to create a scenario in which the yandere may suspect your fidelity. Her reaction to this will settle her as a yandere -- violent outbursts, jealous rages against the other girl, etc.
10. Pacify with sex. Congratulations, you are now attached to the rarest and finest of all sex types!
[color=red][font=arial black]Yandere Guide Part 2 - Maintaining her[/font][/color]
Know how to maintain your yandere, it could save your life (and your neighbour's)!
1. Becomes unusually aggressive in seeking sex, she's probably done something bad and is now looking to celebrate her latest victory over the forces trying to take you away from her or ruin her happiness.
2. Becoming obnoxiously chatty, it means she's becoming stressed but it's not at the critical phase yet. Fix with some attention and re-assurances.
3. Stalks you -- this is absolutely normal behavior for her; if she couldn't stalk you she would become quickly stressed.
4. Gets angry at you: her yanderu is emerging, and it's now critical that you bring her back down. Provide re-assurances, attention and sex constantly until she has no more signs of stress.
5. Becomes abnormally illogical or displays strange behavior: she is at the breaking point and is about to have a psychotic episode. Her emotions are in control at this point, and she's suffering greatly. She must be detained and made to hear your voice or she will eventually collapse.
6. Loses the light out of her pupils: she's lost it and she knows she can kill. She's fallen to a psychotic episode and in an effort to take back control of her mind she surrenders to her emotional impulse to kill, destroy or hurt. In this state she has more presence of mind, but her logic will become almost child-like. You must not display any fear or weakness, and you must talk to her gently while holding her gaze firmly. Her episode will subside.
To end off, some related images of a well-known yandere:
Enjoy! :D