I have noticed many agents do not do their homework when it comes to listing a property on the Multiple Listing Service.  When acquiring a new listing it does not take much to do the research and get answers.  When you have a new listing, find out what tract it is located in.  Don't fill out "other" or "custom" when the tract actually has a name.  Many agents research areas by the tracts because their buyers like a particular area and not always Thomas guide numbers, which means they will miss your listing.  Be as accurate as possible, ask questions, get answers.  What school district is it in, elementary, middle & high school?  Many home buyers are looking for their children to attend certain schools or districts.  Supplying this information only makes your listing a better selling listing. 

As for photos...carry a camera with you at all times just in case!  When you first post your new listing it goes out to all the individuals who are prospecting a property just like the one you have listed.  Adding a simple exterior photo gets that many more people interested.  If you don't have a photo on your listing, it is easier for interested parties to delete and write off the property believing the property has something to hide.  Don't use your cell phone camera to take pictures.  Sure they have come along way, but the quality is just not there yet.  Be as through as you can be when entering a listing into the MLS.  It will only give you a better chance of selling the property and giving the homeowner what they rightly deserve.   

What else do you see missing from the MLS that you want agents to fill in correctly?