Appearing distracted during an interview can be a big mistake. The person who is interviewing you will be looking for signs that you are engaged in the conversation, such as eye contact and quick responses. Attending to them shows the professionalism that is expected in this type of situation, and if they don't think you are listening, you probably won't be considered for the position.
So what are some ways you may appear uninterested? The number one thing to watch out for is your cell phone. It is vital that you turn it off prior to an interview, so check this--and double-check it when you get to the building. It doesn't matter if you are hoping to get a creative director job or one as an editorial assistant; a ringing phone will leave you off the hire list pretty darn quick.
Your watch is another potential issue. If it chimes on the hour, turn the feature off--or ask someone to do it for you if you aren't sure how. Also, don't check the time at all while you are speaking with the person who is interviewing you; they may find it rude. Fidgeting is another thing to keep an eye out for as it can make you look either bored or nervous.