Sorry for late reply, i was traveling.
Well genjutsu is the art of illusions, it 'uses' the performers own chakra to manipulate one or more? of the opponents senses, which are sight, touch, sound, smell, and taste, with the last two being the least two to be used, smell will be mostly used by inuzuka clan members, as there ninken can produce a nasty smell which can trap the opponent, taste is a tricky subject, as one must place the food/substance on the opponents tongues, and unless your orochimaru or mister god mode/speed of light mover, you will find this extremely difficult and almost impossible. Genjutsu based on Sound is special to sound release users, and musical instruments users, so it is rarely seen to be used. Touch is also a way to place genjutsu so it is suitable for close quarter range fighters, the user will have to touch the opponent to induce the genjutsu, the last and most used way to place someone in a genjutsu, is using the opponents sight against them, a common example is the infamous bringer of darkness, sight based genjutsu is almost useless against sharingan users.