Not a surprise, right? Arriving on time shows respect for your interviewer's time and gives a preview of what they can expect should they hire you. Give yourself plenty of time to accommodate for anything unexpected (e.g. construction, traffic, etc.). If you get there more than 15 minutes early, you can always use the extra time to prepare in the car.
having your phone in sight
A 2014 study from the journal of “Social Psychology” found having your cell phone visible may distract you from complex tasks. Makes sense. How often do you check your phone each day — even if it's just a glance? This supports previous findings that even when you don't engage with your phone it reduces the quality of social interaction. And really, we don't need research to confirm that having a phone out in an interview doesn't reflect well on our professionalism and general level of courtesy. Turn it off and save it for after the interview.
Even if it becomes clear this position is not a good fit, give the interviewer your full attention and best effort. This person may be so impressed, they consider you for another position now or in the future. Make eye contact. Sit up straight. Be pleasant and professional. Be the person you would want to interview.
stumbling to explain resume gaps or why you left a position
Companies are not looking for job hoppers. Everyone encounters layoffs, relocations, changes in their career, etc. But having a new job every year can show a lack of self-awareness and dedication. Spend some time writing down the circumstances of your job changes, then rehearse them out loud and in front of a mirror. Be frank while casting the best light on your intentions now and moving forward.