A warm up song is like a first impression. The first song that your students hear is going to set the tone for the rest of your class. You always want make sure you put some thought into your first song. I like to choose fast paced tunes with a great beat that make people smile.
I most often will choose songs that are familiar for the warm ups. Some times it's a newer release, but I also like to find classics that people may not have heard in a while. One way to keep familiar songs fresh is to use a remix or a mash-up. I love this Led Zeppelin/Doobie Brothers mashup. It combines two old favorites: Led Zeppelin's Trampled Under Foot, and the Doobie's classic Long Train Runnin'. At 4:27, it's perfect for a fast paced, in the saddle warm up.