Assuming you already have job experience and are not a new graduate or entry level job candidate, the absolute most important section of your resume is your current or most recent job information.
This is typically the first thing a hiring manager will look at when deciding whether to bring you on-site for an interview.
Education, career summaries, career objectives and previous positions are all secondary in comparison to details about your current role, and will often be skimmed over by the hiring manager on his/her first pass of your resume.
Because of this, you should put as much eye-grabbing information as possible in your current work section to attract the reader's attention.
The information written in this section should include key responsibilities in your current role, but also some of your achievements and accomplishments. The new trend in resumes is to focus on actual accomplishments rather than what you were responsible for or what you were supposed to be accomplishing.
If you've achieved something significant in your current job, don't list it in a career summary or introduction paragraph on your resume. The best way to emphasize this work is to list it as one of the first bullet points under your current position.
If you held multiple positions with your current company, you can show your career progression by listing your job titles and dates for each separate position in your current employment section too.
When the hiring manager reads this section (often before anything else), he/she will quickly be able to see your career progression and how you advanced within your current company.
If you've only held one position within your current company, that's fine too. Either way, you should focus on accomplishments and write as many interesting fact-filled bullet points as possible.
Remember that the purpose of a resume is to show the necessary qualifications and experience to get invited for an interview. In order to do that, your resume has to be attention-grabbing, and the best place to focus on accomplishing this is the first place the hiring manager looks.
Before anything else, focus on your current work section and you will greatly increase the amount of interviews you receive.