Help with a fanfic

[Guernsey]

Hello, I am trying to start a crossover fanfic with Mai Otome with Final Fantasy VIII but to be honest I don't where or how to start his considering this is just one of my attempts at a crossover fic. I am not that eloquent of a writer and I had seen my fair share of crossover fics but I want to try and avoid the same mistakes that authors made in other crossover fanfics although that may not be possible since it has been along since I had written a story. Do any writers here have any tips on how to describe people, places and objects? I have a hard time with things like those and most of the time I either put too much detail or too little.