I get asked about how I choreograph quite often. Here are my go to tips for anyone who wants to make up their own dance at home.
Listen: Turn on your song, and envision what you'd like to do. Listening to the song, creating counts, patterns, and a connection to what drew you to the song is a great musicality practice.
Record: Grab your music and your camera. Recording yourself dancing feels like listening to the sound of your own voice(icky); however, once you can get comfortable watching yourself move you're going to learn and grow a lot more. So for your first take, turn on your music and just move with no real expectation. Often this is where I get an outline for my dances.
Watch: This is the hardest part. Watch back what you just worked on. There may be things you hate, but there also may be things you love. Sometimes just the idea of a move is created here and it expands and grows into a full eight count, or measure.
Write It Down: While I'm creating I write notes to help remind me of what I was doing so I don't have to focus as much attention on memorizing the routine up front. Leave your mind space to create, memorization comes later.
Record Again!: Once you've got a whole routine prepared make sure to record it again. Having notes and a video helps to keep this artwork documented and teachable or shareable. It sucks to do all that work and it just disappear the second you forget it, trust me.