If you want to sell quickly, you must have a better-looking house than your competition.  Buyers like to visualize themselves in your home.  You can talk until you're hoarse pointing out how much better the house will look with a coat of paint, but, until it's painted, the buyers simply won't see it.  Therefore, fix it up.  Paint and basic landscaping are a must.  Here is a quck list of fix up items...

Assuming that you're not trying to rehab your property, a good rule-of-thumb is to do those things that are inexpensive first, then work outward from there.  Paint, wallpaper, flowers/shrubs/lawn and getting red of debris all count.  Do these simple things and it will make a world of difference to every potential buyer.