Anything longer is an autobiography, not a resume. Don't overwhelm employers with information. Hence, you will need more than one resume if applying for different types of jobs. If you are applying for a Child Care Counselor job, devote more space to your experience as Camp Counselor. But if you're applying for a job as a Management Trainee, condense that and emphasize organizational and supervisory abilities.
Most employers call to set up an interview.
Seldom will they write. Hence, make sure they have a phone number. Two of the more common formats, the Chronological and Functional are briefly described below. Each has certain advantages and disadvantages. The format you choose will depend upon your specific circumstances and background.