I have been doing my own music charts on and off for over 30 years now. The genres of music have changed over the years as my tastes grew and changed, but the methodology has pretty much stayed the same. In general, it's based on airplay, internet radio, television music video stations and any other media where I'm not choosing the songs to play. Each airing gets a point. In addition, there are some stability factors also included.
I got started doing my own charts in high school. I used to listen to the countdown on the radio every Monday night and write down every song as the DJ announced them. Then I noticed that what the radio station was actually playing wasn't anything like what the charts they played on Monday nights. That's when I started doing my own charts to reflect what was actually being played.