Price items with pictures.
State your specific price. Note whether it is firm or best offer.
Only one item per listing.
Make the subject heading indicate exactly what you are selling.
To avoid spammers and con artists - state local pick ups only. Cash only.
Be real about your pricing. I don't care that you paid $500 for the chair 10 years ago. You are only going to get MAX $50 for it now. Maybe less. Probably less. Be glad that you don't have to pay to get someone to take it away for you. Sorry....
You may need to post several times. Most people do not look past the first two pages when searching. I've had people tell me that they posted on Craigslist and "nothing happened" but when I asked more questions I found out that they only posted once and without a picture because it was "too much trouble."
Make sure that your spelling and grammar are correct in your ad. It makes you sound more real and honest. Don't use your real email. Use the made up ones that you get from Craigslist. You can use your real email when you respond to specific inquiries.
Hope this helps.