Send cartoon syndicates copies of between 12-24 strips (two to four weeks worth of dailies). The strips should be reductions, to the size they'd be printed in a newspaper or book collection (not only will this give syndicates a better idea of what your work looks like than full-size copies, it'll cost you less in postage). Some sydicates want to see two to four Sunday strips as well - just the black and white art is fine. Make sure to put your name and address on every sheet of paper, including the copies of your strip. Never, ever send originals.
Don't worry about your ideas being stolen - if you're that good, syndicates will want to use you, not alienate you.
You can also include a one or (at most) two page description of the strip's concept, the important characters, and future directions you have in mind for the strip. Be brief and punchy - remember, the person reading your submission has an immense pile of submissions to get through, and you won't make a good impression sending something that takes longer than your competition to read.
If your cartoon is published in any newspapers, or if you have any publishing "credits" at all, mention that in the cover letter, but be brief. You're establishing that you're a professional, not sending a resume.
Make sure to include a self-addressed stamped envelope, and expect to wait a while for a response - most syndicates receive five or six thousand submissions every year (out of which they accept maybe two or three), and reading and replying to them all takes time. It's acceptable to send copies simultaneously to all the syndicates - here's a link to a list of syndicate addresses.
That's it! Good luck.
Back to The How-To Guide to Comics