I think the best way is to just do it! Just starting to put moves together, and fiddling around with music is good. Normally I'll just put on a piece of music, dance to it a few times without thinking, before stepping back and really thinking about how I'm going to progress through the music. It took me a while to start choreographies when I started dancing, and I did a lot that I have never performed! But just practice and let yourself have fun with it. It gets easier, at least I think it does. I usually film myself too, because sometimes it looks different then it feels. Just have fun, I think thats the main thing, because then the routine comes out looking natural, rather than looking as if you have rehearsed every single second a million times.