Employers can take as little as thirty seconds to decide whether to toss your resume or to call you for an interview.  That's why it's important to make it as short and catchy as possible while still showing off your achievements.  Here's how your can cut the fat.

Define your goal.  Why are you writing this resume anyway?  Be specific about the job that you are trying to get.  If possible name the actual job title.  If you have more than one dream job, write a tailored resume for each.

Include details that support your goal and take out everything else. That means that if you're trying to get a job as a private trumpet teacher at a high school, include your experience playing in the wind ensemble at music camp, but not your summer job as a sandwich artist.  Even if you got paid to make subs, and you had to pay to play in the band, the camp is related experience and the summer job will be a distraction.

Prioritize. Include your most impressive accomplishments, and cut the minor ones that don't fit.

Edit each bullet point.  If there's more than one action verb in a bullet point, arrange the sentence so that the most impressive part is in the front. Cut out all unnecessary words and phrases.  Make sure that you haven't said the same thing twice (If you have similar experience in two different jobs, try to highlight different skills).

If all else fails, adjust the font.  But don't go below 10 pt.