When submitting work to magazines, you will want to read the specific guidelines for each publication. If you are unsure how to format your work and the publication does not explain, consider using these standard guidelines as the default. I found them long ago in a print copy of Writer's Market and have adapted them. Long ago, that book was my writer's Bible, now much of the information can be found online.
Formatting for Fiction Submission
If you are submitting fiction, most likely the publishers will want your work to be formatted something like this. Use 12 pt. Times or Georgia or Helvetica or Arial. No fancy fonts. Double space the lines. Only one space after a period.
Upper left corner (single spaced)
City, State, Zip
Upper right corner
Footer (unless requested to omit name for blind jurying)
Last Name - Title or Key Words - Page Number
Formatting for Poetry
Use the same upper left corner block as above. In upper right corner, instead of word count, use line count. Footer is not necessary unless one poem is more than one page. Use 12 pt. Times or Georgia or Helvetica or Arial. No fancy fonts. Single space the lines.
Artists, consider sending your work to magazines! Think of it as a way to advertise your art and connect with writers. Look for guidelines regarding dimensions, ppi and jpg or tiff. If the mag is web only, then 72 ppi will be fine. If print, then 300 ppi. See if they want 4x6 or 8x10, by total Ms or how many pixels on the largest/smallest size. It is recommended that you have Photoshop skills. If you aren't sure, this tutorial looks good.
Your cover letter is just that: an introduction. Most are placed in a little box on a submissions website, so keep it simple. For some ideas about what you should and should not include in your bio, see this post. When submitting short written pieces or art to a magazine, you don't need to include much information in the cover letter unless the publisher specifies more in the guidelines. Always read the guidelines.
All flush left (single spaced)
Dear Fiction Editor (or Editor's first and last name if you know it),
Thank you for considering my story, "(Put it in Quotations.)" My bio is below.
(Start your bio with your full name. Include highlights of relevant work and publishing information as well as your geographical location. Keep the total word count between about 50-100 words. Each publisher may want slightly more or slightly less. Always, always read the guidelines carefully.)
Your full name
City, State, Zip
You can find listings for magazines at Duotrope and Everyday Fiction and New Pages, among others. Good luck!
Note: A query letter is different from a cover letter. If you are requested to query first, then you would send a brief synopsis or summary of the piece, written in a way to hook the reader. Queries are most often requested for full length manuscripts, however.