Understandable.
The methods to breaking genjutsus are 1. Pain based releases, 2. Full Body chakra surges, 3. An external source of chakra/energy.
Pain based releases affect the balance of yin to yang energies (or spiritual and physical energies) by disturbing your physical energy through induction of injury. Physical pain is enough to mentally shock you into reality, which is naturally done in real life, something like "knocked back to reality". Because some genjutsus are more complex than others, it requires a higher level of pain to break the genjutsu.
Full body surges are as the name suggests, full body surges of chakra, used to both "flush" the foreign chakra from your body and create a secondary attack or defense as most full body surges serve a second purpose. This works because your chakra flow sharply fluctuates to increase the amount of your own chakra present and as a result, it forces the enemy's chakra out. Now, if your full surge of chakra isn't stronger than the illusion you're in, then you do not break the illusion.
And, my favorite, the external source of chakra. With an external source, you can flush your chakra flow of the enemy's chakra by altering the chakra flow through induction of said external source. The most known example in our RP would be the Nekura and the induction of Juubi chakra constantly flowing and surging through us to prevent external genjutsu sources to enter.
Now, those are the only 3 ways I know of. Unless you are speaking about if one should attack the genjutsu they are in, causing it's effect to cease and end. Or if one has a Sharingan which is able to pierce through a multitude of visual based genjutsus. Or something else completely. o-o