How do you remove a spell off of someone else?

You can either;

Cast a protection spell on the person who the spell has been cast on--including yourself. Be careful with these, though, and try to use strictly Wiccan ones of minimal malevolent intent

Cast a binding spell on the original caster to prevent them from casting more black magic spells that could hurt other people.

A Witch's Answer

I do not recommend the uninitiated undertake either suggestions in the answer above. Much as both suggestions are what the "outside world" expect as answers, Witchcraft is not a game, nor is it something you can take on without years of study and practice. Witchcraft is an ancient spiritual path (religion) and it makes no more sense for someone who is not a practitioner to attempt this than it is for them you undertake an exorcism.

If you are already a practitioner, then you do not need to be told how to do things, your mentor, High Priestess/High Priest, or Teacher can walk you through it.

Trying to cast a protection spell without training and the knowledge and permission of the subject will only put you in the way of the Rule of Three, no matter your intent, it is still manipulation. As for binding spells, these are the very worst kind of manipulative spells. Making someone do your will is NEVER good.

If you are the one who cast the spell - refer to your Book of Shadows, and do a reversal.

If you are the one who has had the spell cast upon you.

First be sure you actually have been spelled. A run of bad luck, or someone telling you they have cast a spell on you does not mean it has in fact happened.

In witchcraft it is not just advisable, but essential to have the complete knowledge and express permission of the one you are casting on/for. Anything else smacks of manipulation, is basically unethical and puts the caster in the way of the Rule of Three. (That which you send out will return to you three-fold).

- Your personal belief system (or will) is your best protection from a spell. If you do not believe in it, or if you believe your chosen deity will protect you, you are in no danger.