Avada Kedavra

This is one of the unforgivable curses deemed by the Ministry of Magic, and also would be deemed so by most people's personal code of ethics, however it could be used in defense in the sort of case where there is a wild bear chasing you or something of that nature. Anyway to cast it clear your mind and visualize a vital problem going wrong within the target that would result in death such as sizzling the brain, squeezing the heart, blocking the airways, asphyxiation, etc and once that image of the target dying and is then dead in mind clearly release that spell toward the target. If done successfully it should take effect.

Crucio

This is another of the unforgivable curses deemed by the Ministry of Magic, ans also by most people's personal code of ethics. This is the torture curse. To cast it clear your mind and visualize your target writhing in agony know they are experiencing absolute pain, visualize what causes it and magnify it in your mind. then flick your wand at the target and let them be cursed.

Imperio

This is the third unforgivable curse deemed by the Ministry of Magic and also debatable by people due to how it is used. This is essentially a mind-control spell. You can use it to help someone who is unaware of what is ahead or what they are doing. Or of course to lead someone to their demise and undoing. Clear your mind and project your will into their body to override their own free will and give them unshakable urges and ideas to do something you want them to do.

Finite / Finite Incantatem

This spell ends the effects of a spell (it will not reverse death though). To cast it wave the wand counter clockwise while visualizing the effects of the spell gone, everything is back to how it once was. This also can be used on mundane things- if you want someone to end a conversation or relationship. If you want rain to cease, or bad luck streak to end. If you want a situation over with, etc.

Deletrius

This spell works similarly to Finite/ Finite Incantatem however this can be used to 'delete' or destroy effects of a spell or curse such as if a monster was summoned, etc.

Obliviate

This is known as the memory charm. It erases memories; either all memories or specific ones. To cast it visualize an image form of a memory in your mind or someone else's mind and see it fade away into nothingness once it is gone turn your wand counter clockwise in the direction of the target and recite the spell. The memory will within a short period of time (within near future) have been forgotten about.

Legilimens

This is the mind-reading spell. Can act as a substitute or enhancer for telepathy. It allows the caster to invade the minds of whomever they choose it can be blocked by a number of protective spells or practicing occlumency.

Maledicto

This is a basic generic hex or curse- just specify in your mind what the curse is.