Think carefully about whether you want to broadcast your phone number.
Some find the response is more than they counted on, and their phone rings off
the hook.
Remember that you're writing for an audience that will include hundreds—perhaps thousands—of people. Just keep it conversational, simple, and short.
Job posters, please mention the geographic location of the job when
possible.
If you're selling something, tell people more or less where you live,
that'll make life easier for you and whoever might want to buy.
If you're posting an apartment, condo or room for rent, you may want to provide
the cross streets. Often people are not familiar
with the area or are looking to move to specific neighborhood, providing this information
will help folks out a lot.
Use descriptive terms about your item that will help buyers searching the site to find it. For example, use the word "dog" in the description in addition to the more specific "Scottish terrier."