First and foremost, you want a show reel. Show reels are recordings of you expressing your talent to the world. Typically, these are excerpts from songs of previous gigs instead of full songs. A good starting number is three to four tracks showing your full range and versatility. Try to have at least one track showing that you can harmonize and improvise. Next is a biography boasting your experiences and accomplishments. These experiences should be past gigs that have the name of the act you worked with and the place you sung at.
Make sure your separate gigs between venue types, such as on TV, on a movie or in a live performance. Although this is more important for live performers, having a photograph pus a name to a face and is just a good element to have on your profile. Make sure the photo is a professional and shows that you’re happy. Lastly, attention to detail is a vital skill of any backup singer as you will have to be extremely precise to copy or harmonize with another singer. If you’re not good at this, continue working at your musicality and technique. A good ear is invaluable in this industry.