Because everyone wants to avoid the spam & scams that plague Craigslist.org
So, first things first. To get directly to your city on Craigslist, in your address bar type Your-city-name before dot-craigslist-dot-org. Like this: newyork.craigslist.org which will take you to the New York City page.
Next thing you want to keep in mind is to keep a look out for scams. Easier said then done right? Not so.
1) Look for names. If the add asks you to put it to the attention to a specific person the chances are it's a real ad. The same for if there is an e-mail or mailing address that they ask you to respond to.
2) Read the ad and follow any directions it might have. It the add says to send it attention 'specific person' or to add a specific job number, do it. Put it in the subject of your e-mail and in your cover letter. This shows them that you can follow basic instructions and thus shouldn't get you weeded out of the running.
3) Avoid ads that offer to pay way higher then the going rate in your area. If in your area your job lands you $10 and the post is offering $20? Chances are it is not legit.
4) Watch out for duplicate ads. Sometimes the scams will use the same format for the same position and post many times. Some sneaky hiring agents do the same thing. After a while you will notice that some look exactly like ones from the last time you looked and while the location might change chances are they are a scam. Also, Craigslist has a 30 day rule which is basically that you can't post the same ad with in 30 days of your last post. A handy little thing to keep in mind.
5) Watch their grammar in both the subject and the body of the ad. Most are gimmicks to get you to apply, they are pretty obvious but some might sneak past your watch. There are some people who are legitimately bad at making postings. These are usually done by people that are not used to looking to fill an opening, by people who don't really use the internet or just someone having a bad day.
It's not a long list but if you keep these things in mind when job hunting on craigslist they could make you search a little bit easier. I use all of these methods in my own searches and I use them as I discovered them. I have gotten more call backs using this list then I have just replying at random.