Personalized for each job position you are looking for, nicely formatted and well organized, all the main data on the first page (often the big part of recruiters do not even read the other pages), at least one link to something (your github/sourceforge/personal_blog/etc) in which they can see some exemples of your code/coding_style and if you have a list of other jobs you have done in your life please put first a list of those strongly related to the job position you are looking for now, then a second list with all the others.
No. It'll either help you more or hinder you more.
Make it a nonfactor by not putting one on there. They'll validate your merits without doing that. It's okay to put one on a portfolio - HR and future bosses don't look at the portfolio first. They'll do that if your resume is up to snuff.