The summary section of your resume is very important; it ties everything in your resume together in one neat little package that's easy to read but still has all the information a hiring manager wants. Done well, the summary section can be a nice ribbon on the package of your resume; done poorly, and it tells the hiring manager you don't know how to wrap things up. Here are some dos and don'ts for your summary.
DO: Sum up your career in a few short lines.
Your summary section should be 4-6 lines overall, with general, overarching titles and descriptions of what you're capable of doing. You don't want to write down everything you learned or did in the course of your career, but list your main competencies. If your resume includes keywords, and it should, this would be a good place to put them.
DON'T: Take up too much space in your summary section.
You don't want your summary to take up the bulk of your resume page. Your cover letter can expand upon your summary section, but on the resume itself, you don't need it to be more than an average-sized paragraph. If you don't condense it down to a few lines of high-quality descriptive terms, it'll show hiring managers that you're not selective at how you present yourself.
DO: Keep it succinct.
A list of competencies and a few descriptive words is sufficient for your summary. You don't want to go overboard and list everything you've ever done; you want to highlight everything that you do well or regularly. If it's something you don't like to do, don't excel at, only did once, or it's not in the job description, leave it out.
DON'T: Sell yourself short.
Be sure not to err on the side of under-inclusiveness, however. You want to make sure the hiring manager knows what you're made of and can get a good idea of what you're good at. Don't leave something out if you think it their knowing about it would make you a more attractive candidate.
DO: Include relevant competencies and certifications.
In your profession, there are likely certain programs, platforms, or tasks you're familiar with. Here is the place to list them, although they may appear in the body of your resume as well. If there are certifications required within your field or that you think would make you a better candidate for the position, the summary section is a good place for them to go as well.
DON'T: Add non-sequitur information.
In your application for a project manager, it's probably not important for the hiring manager to know you came in second in a cooking tournament, or that you can give Journey a run for its money on karaoke night. Keep it relevant; while some hobbies may make a resume look better to hiring managers, keep personal, non-relevant information out of your summary section.
Summing up your resume should give the hiring manager a general outline of who you are as a worker, what you come from, and what you're capable of. It doesn't need to be specific, though it should be as thorough as possible. It's important that when writing the summary section of your resume that you keep in mind how this section is presenting you: does each item in your summary give a general view of something you discussed more in-depth in your resume or cover letter? Try LiveCareer's Resume Builder to find more information about writing a killer summary section.