I remember when I was a teenager, my sister brought her boyfriend home. Later he became my brother in law, and still is. I remember he came up to me and introduced himself, I gave him a wimpy handshake. He looked at me and said "That's not how you shake a hand, this is how you shake a hand." I'm not sure why, but it left a lasting impression on me.
The ability to look someone in the eye, give them a firm hand shake and talk to them with a confident voice is very important. My brother in law taught me that as a young teenager, and I try and bring the same lesson to all our students.
Don't overlook family members. Taking a few moments out of your day to connect is even more important with family. With certain family members maybe it's a hug instead of a handshake, and that's ok. Just make sure you are taking the time greet them.