1. Use ebay & money in your subject heading. It will increase your open rate by 67%
2. Go here to find the hottest cities to post in:
http://www.google.com/trends?q=Craigslist.org
3. Have 30 ads and rotate them every day. Post at least in 5 cities every day.
4. Change your image links every 3 to 4 days. You can use the same image but change the directory.
5. Keep track of ads & cities in a spreadsheet.
Good luck!!!!