When creating a professional model portfolio, you want to include as many versatile shots as possible. Some Agencies provide model hopefuls with specific criteria to include, such as editorial shots, bridal, body shots and/or headshots. Your portfolio can make a difference on whether you book a job or not. It will show a casting director how versatile and professional you are; it should represent your personality and the effort that you are willing to commit to.
If you have experience, your portfolio can be done in one session. Some experts recommend having your portfolio be a creation of multiple sessions and shots and most importantly to keep it up to date.