In an interview situation being friendly is great--but being too personal is inappropriate. At times this may feel like a fine line to walk, but there are some simple guidelines you can follow that will help keep you from crossing the line. Some things are fairly obvious; for example if you are asked how you got started as a graphic production artist you won't want to point out that your first boyfriend took classes with you which made the training fun. Instead, stick to the subject and don't embellish with personal information.
If you can think of friendly as more of an attitude, it might be helpful. Getting into the particulars about your home life, hobbies and opinions really isn't appropriate for a job interview. Friendly means that you are providing information to the interviewer that will help them decide if you are qualified for the job and a good fit for the company. If a response doesn't fit into those categories, you may want to think twice before saying it.
If you tend to have difficulty with this type of thing, it may help to practice interviewing with someone you know. Have them point out when you are getting too personal, and work on sticking to the facts in a friendly manner. In time you'll be better able to see when you are getting off-track and learn to relay your information more appropriately.