Pictures are a must. Many buyers don't look at ads without photos. It helps if the camera can get a clear photo (macro lens setting?) of the label plate data.
Spell check. Some buyers only search by keywords, so use as many different keywords as you can fit in your ad.
If applicable, "EnergyStar" is a great keyword.
No such thing as too much info-- do the work for your buyer and it helps to weed out the tire-kickers & flakes. Details that are appreciated are manufacturer, model, model year, all dimensions (including brackets & trim pieces), any other identifying data like capacity or blade size, and all ratings. If you can link to a manufacturer's website or an online owner's manual-- especially for electrical equipment-- then it's a bonus.
If you have documentation then mention it. If you don't have documentation then mention that too and provide links. If you have spare parts or remote controls or extra accessories then include that to separate your offer from everyone else's. It saves the buyer a lot of time trying to figure out if they can assemble a complete set from your pieces.
We usually say "Loading assistance available. Sorry no delivery." You might also want to say "Cash only." If you want to deliver then say so, and if you want extra money for that then say so too. It helps a buyer who may not be able to get a truck.
Depending on your comfort level, a phone number as well as the Craigslist e-mail address will move things along much faster. Our local Craigslist either has an RSS feed or a bunch of vultures-- sometimes our post has just hit the server when our phone rings.
Don't get caught by surprise when your buyer needs directions. An address for Google or Mapquest is great, but street names and turning directions are an unexpected bonus. I don't know how many sellers have posted their ads and never thought that they might need to (1) give out their address or (2) give directions. Another alternative is to meet at the parking lot of a store at a certain time, which is far better handled by cell phone for the inevitable delays & MIAs.
There are several Craigslist scams discussed on their website FAQs. One of the more popular ones is to send you a cashier's check and have someone else "pick up" your merchandise. Of course the cashier's check is a forgery. We've only ever had one Craigslist buyer who didn't pick up in person, but they agreed to wait until their check cleared before we mailed the item.
If you're going to be accepting $100 bills then it might be worth getting one of the counterfeit-detecting marker pens. We prefer thick wads of $20s.
Depending on local custom, your price may not be the actual price. Around here when we say $100 we mean $100 but in other areas that may be the opening bid on a $75 sale.
When we post an ad, we generally only update it after one or two weeks. Most buyers search for keywords or neighborhoods or categories so if it's a couple weeks old it may still show up on the first screen or two. Beyond a couple weeks, though, buyers may assume that your merchandise is crap or that you're too lazy to take down your post.
Another popular scam is gift cards. If you decide to buy a gift card (usually sold at 70-80% of face value) then use it immediately after verifying that it's valid. Otherwise the seller may have fraudulently bought it with a store account or a credit card and the store will cancel the gift card without notifying you.
It is not illegal to sell frequent flyer miles through Craigslist. If the airline figures out what's going on, though, they will make it impossible for you to board your non-refundable flight. They will also penalize the seller of the miles.
And unless you have hours of spare time, do not read Craigslist "best of"!
