Posting ads on Craigslist is not only cost effective, but it also only needs to take a minute or two of your day. Once you have all your ads actively running, all you need to do is renew or repost your ad.
For starters, most of the time your ads will have a renew link in which you can bring an actively running ad to the top of the search results. This table is displayed once you log in. Your active ads will be highlighted in green with the newest postings being at the top. Each day, all you need to do is log in and renew the bottom green ad (the oldest active ad).
To prevent spam robots from auto-posting, Craigslist will periodically remove the renew link from some of your ads. When this happens, you will have to click the 'delete' link and repost the ad. This involves a couple of extra steps but will also not take more than a couple of minutes or two.
What is really nice about this feature is that Craigslist automatically stores copies of your ads for you. This is especially handy when using html formatted ads. After creating an ad for the first time, it's still best to save it as a backup on you computer. To do this, simply open Notepad, copy the html code, then save the file. This is useful in keeping a backup copy of your ads. You can also go Edit/Modify page, copy & paste your ad, and make changes in the future. This is much better than having to start each ad from scratch.
Each Ad Must be Unique
If you have multiple ads running at once, be sure each ad is unique. If you post an ad that is very similar to another ad you already have running, Craigslist will not allow you to run it. Their server checks for duplicate content.
If you run into this problem, I would recommend by focusing on your different products and different target markets. For example, imagine you're a tax accountant. You can have one ad targeted for individual taxpayers who need their income taxes prepared. You can craft another ad targeted to small businesses for accounting services. From here, you can offer an ad that reveals how taxpayers can deal with IRS problems. Think of different problems and different needs that your client base has. Then, draft an ad that specifically meets those needs.
Once you have created a collection of at least 5 ads, the hard work is done. The initial effort you put into these is critical. You should spend a significant amount of time drafting and revising your ads. Once they are done well, all you have left to do on a regular basis is to renew them. This is where persistence pays off. People who post consistently will get great results.