Reiki is Universal Energy. Which is basically of God or whomever your religion believes in. I happen to believe in God. My understanding of God is that he doesn't want us to suffer pain and hardships. So with Reiki I help heal people of the pain and hardships. What I did with my neighbors is helped them solve their problems in what was making them miserable as well as us who live here. Now they can be happy and have a good place for their children and we can have a good place to live without their negativety.
I do the same with my two neighbors behind me when they play their loud music. Instead of calling the police when my windows are rattling, which then breeds more negativety.. I ask that they be able to work out their problems so that we all can live in harmony. Intent is the key, and for me to use it, it has to be for their highest good. Their highest good isn't scaring them, but showing them love and compassion, as well as helping them deal with their problems better. Besides, negativety breeds negativety and positivety breeds positivety.
You can use visualization to help with sending reiki to someone. Sometimes I visualize their mobile home because some I know what their homes look like versus themselves, and others I visualize the people and send it to them. But for me, I use visualization all of the time when I send by distant.