You should end a relationship by the highest level of contact you have previously had--if you have never talked, by email or text is fine I guess. If you have talked on the phone it should be on the phone, if you have been together in person, it should be in person.
It doesn't make sense in a LDR to make a special trip to break up with someone, unless it has been a long term relationship. Regardless, as you mentioned somewhere in another post, if you use a "it's not you, it's me" (paraphrase) approach, it will go over better. Maintain a person's dignity, however the break up has to happen.