More than One...

Well, the biggest mistake that candidates can make is having only one. Keeping your resume to only one page when their history and skills can command two or three pages, and having only one version of the resume.

Look if you have a lot of skill sets and have multiple years using them, then don't just summarize and send to the company. Now this is a slippery slope. You don't want to add too much, but you don't want to not add the right things. What you do is find out what the job you are applying to is asking for and make sure the needed skills are high lighted, talked about, and detailed in your resume (as long as you have the skill-set). I am not saying be dishonest on your resume, I am saying make dang sure the person reading your resume, which is usually an HR person who is only looking for key words, can tell right away why you are a great fit for the role.

HR doesn't care that you have six years of project management skills when the role you are applying to is a Sr. BA and nowhere on the posting does is say, "Must have PM skills". Plus HR is not big on reading all the way through resumes.

Bottom line. Match up your resume to what the posting is asking for, and then detail, highlight, and make sure the skills are toward the top of the resume.