Well, before we move forward, you should know that hypnosis in the RP is a tricky topic.
Hypnosis is essentially tapping into the more primal levels of your mind. To explain, the mind is similar to an onion, with layers and layers of thoughts, emotions, feelings, etc. These layers are held together by the will of the person. This will can be manipulated and shut down through hypnosis, causing them to revert back to this primal sense of control. This can largely be done via Sharingan genjutsu, but on a smaller more specific scale, it can be done without genjutsu. It always requires eye contact and this contact must be sustained. Through this eye contact, you can alter how they see and perceive basic things, changing them to suit your needs. You can for example alter their perception of time, like when Kakashi fought Zabuza like Imp said ( though, Zabuza performed the jutsu, Kakashi made it seem as if he was performing the seals at the same time, suggesting he could read his mind ), you can alter feelings and suggest words into their mind, which can make it seem as if you can read his mind. With this, you can play around and toy around with their mind, but you can never bend their mind to the point that you manipulate their free will or body. It's ideal for taijutsu means, altering their sense of time perception to make it appear as if you are attacking at the same time as he is. But the true usage of it comes from it's roleplaying aspects, roleplaying not as in Battling, but roleplaying as in character development and such lol. Like you can hypnotize them into feeling fear, anger, anxiety, etc etc, and from a RP standpoint, that's a pretty cool thing to make use of in a battle. Of course, there is a few limitations to this, namely the fact that you must maintain eye contact continously and the fact that it only works on targets 1 rank and lower from your rank, Sage being able to affect Unofficial Sages and so on and so forth.