Determine what characteristics you are looking for in your future job/company, and be specific. You need to know what it is you are looking for before you will ever find your "dream" job.
Find out the companies dress code before interviewing and dress appropriately. If in doubt, overdress.
Research the company. If possible try the Nasdaq, NYSE, and/or the company's website. Check their financial stability, history, principles, focus, philosophy, etc. You might even try to talk to current employees.
Even with a good excuse, you can negatively impact the way the interviewer sees you if you are not on time. Once you confirm an interview, everything you do from that point on will be judged. This includes the time before, during and after the actual interview.
What you bring to the table should be an incentive for a future employer to make you a job offer. What are your strengths/skills? What are your work accomplishments?
Monitor your interview activities and take good notes. Write down which companies you've sent resumes to, which you have met with, each person you meet and how to contact them in the future. Keep a close record to insure you don't miss out on your "dream" job opportunity.
Most people forget to ask for the job at the end of the interview. Whether you are extremely interested or just mildly interested, it's nice to have the option to accept or decline a position you have been offered. So ask for the job first, and you can decide later whether or not to act on the opportunity.
Thank you notes and follow-up calls may seem old fashioned, but most if not all employers appreciate the effort. A simple note or call will keep your name foremost in their minds.
Research the salary ranges for the opportunity for which you are applying. You do not want to offend your future potential employer by asking too much, however you do not want to short change yourself by asking for too little. Contact HR, company websites, or your recruiter to find out the normal or posted salary ranges for your particular position.
Usually the first place one looks is to HR and while HR can be very valuable it is almost always better to get in front of the hiring manager--the Sales Manager. HR is concerned about staffing all position within a company from Accounting to Sales to Clerical. The Sales Manager is concerned about staffing sales people and getting the best person on his team--his income/bonus usually depends on it.