When writing the descriptions for the jobs you’ve held, focus on what you accomplished in each position rather than what you did. Listing quantifiable achievements in a numerical manner (increased sales 20%, reduced expenses by 10%, for example) will help your resume stand out.
In the short term, you should tweak your resume based on each job you apply to. For example, if one position you’re applying to seems to weigh a certain responsibility or focus over another, you should be sure your resume conveys your expertise in this area. At the same time, you should be updating your resume with your experience as it develops, adding any new skills you’ve learned, courses you’ve taken or awards you won.