Answered by Stephanie, Hiring Expert at AT&T Inc., on Tuesday, September 29, 2015
References are an interesting thing! Who is going to list a reference that would give them a bad review, and yet they are almost always asked for on an application and typically included with a resume package.
You always want to go with people who are going to actually be able to speak to the work you did or do. Typically an employer or agency is going to want to speak to someone who supervised you, so it is a good idea to include a few of those. If you want to show a wider variety of experiences you could also include people who are familiar with your volunteer work, or if this is a first job out of college, a professor who knows you well.
Now part two of your question...you do not want it to be a surprise to someone that you have listed them as a reference. Let them know, let them say no if they wish, let them tell you the best way they can be reached. Then if you do include them on an application or within a resume, make sure to notify them of who might be contacting them and preferably what the job is. They'll be better prepared, and you'll get a better reference. Good luck!