Write every day. Every day. Practice gets you to finished. NaNoWriMo (National Novel Writing Month in November) is a great way to get started and hold yourself accountable.
Fit your genre. I like the action of a science fiction cover. My cover for Mars and Mayhem I think does that with multiple character perspectives dealing with a big problem of alien arrival.
I learned I'm an under-writer and need to write more! I also learned how complex the editing process is. Do some research if you want to go from writer to author. It is easy and doable but take commitment!