We are always sending out our energy. You are a very influential being. If you feel good, you will radiate that goodness. If you feel bad, you will radiate badness.
Sometimes you might want to send a positive vib to a particular person who could use a lift. You have the power to do that with your thoughts, words, and deeds. I believe even your thoughts alone have an influence. As Jeff said, you can imagine them being happy and experiencing what they want.
Abraham-Hicks teachings indicate that when you are appreciating someone, you are connecting to your own inner being.