I was going to go with the "for idiots" (you know - the yellow & black instructional book titles) theme; but decided too many of the intended recipients might take it personally...so I figured ":101" is widely recognizable as the basics.
There are a lot of new members posting really pathetic ads (at least if they want to sell things); but the practice is by no means confined to new users - people that have been around for years are getting horribly lazy, too.
Step 1: Decide what you are selling. (Simple, right?)
Step 2: Use the ad's title to indicate to potential buyers what it is that you are selling.
(Apparently this is a little more difficult; because there are A LOT of people out there that can't manage to do it. If you are posting 4 different color/pattern varieties of the same species, in 4 different ads; don't use the same generic title for each ad...and misspelling a word in different ways doesn't mean you changed the title.)
example:
- GOOD
Adult male hypo motley boa - proven breeder
- POOR
gecko for sell, ball 4 sell, etc
Step 3: Provide information about the animal, including price
Step 4: Provide contact information - how do you want people to reach you?
Step 5:
PUT THE 
PICTURES IN YOUR AD
If you're including a bunch of animals in one ad, it's acceptable to show a few, and provide others to interested parties...but not including any pictures simply doesn't make sense. There aren't many people that are going to purchase sight unseen; so save yourself the aggravation of having to email the pics over and over again. Besides, a lot of buyers are wary of sellers that won't include pictures in the ad. Personally, it would be rare for me to even consider contacting a person that doesn't include images in their ad(s); and I know a lot of other people feel the same way.
Step 5(B): Don't use images pulled off the internet, or from another person's ad(s)...Talk about waving a red flag that says "Don't buy from me"
Step 6: If you don't close your ad, be attentive to replies.
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