Okay, I am no expert, and Im sure others will be able to help you out more as well...but heres my two cents...I hope it helps!
First of all, the cover letter is not really supposed to be an extension of your resume. It should highlight one or two specific reasons you are qualified to fill the position you are applying for...but it still has to be a letter, not a bulleted list of qualities.
Here's a general format:
Dear Hiring Manager/Human Resources Manager/Human Resources Representative/Sir or Madam (its really best if you have a name, but I know it doesnt always work that way),
I am writing in response to your ad in (name of news paper), dated (whenever). I would like to be considered for the position of XXX.
(In the second paragraph you want to show one or two specific skills you have that make you a PRIME candidate for the position. Of course you can be a little more specific depending on the position. You should be able to be a little more detailed in this paragraph.)
(If there is something particular you can offer in the way of training/education you can highlight it in this third paragraph. If there is a person both you and the hiring manager knows you can mention this person in this paragraph, otherwise, just skip this paragraph.)
(In the last paragraph you "submit" your resume and again express your interest in the position, and ASK for an interview..."I have enclosed my resume for your review. I am sure that my experience and skills will make me an excellent addition to your team. I am looking forward to speaking with you about (the position). Please call me at XXX-XXXX at your earliest convenience to schedule an interview.")